I want to start by saying I'm looking at everything here through the lens of the OP. And I plan to go through paragraph by paragraphMileage: I consider averaging over 50mpw an appropriate and sufficient mileage bump for someone who currently runs 35-50mpw now. I would assume that "35-50mpw" actually means current mileage maybe around 40-42mpw at best when averaged over the whole build, with a touch on 50mpw once or twice. Holding 50-62mpw for 10 weeks will do wonders for such a runner. Read back through what he was doing before. This is a substantial diffrence. Intensity: You see "a quarter to a third at MP pace or faster." Leaving aside the fact that it never quite gets to a third, I see no runs even as fast as half marathon pace for like 8-9 weeks in the back half of the program. That's not exactly a HIIT routine. Especially compared to a guy doing 5k and hm-mp work every week right now. Compared to what he is doing now, he'll be much more comfortable at race pace and able to do more mileage than he does now. Further, "too much intensity for the volume" makes more sense if he's doing a lot of 5k-half marathon intensity. MP minus 10s is not that bad for a 3:00-3:20 marathoner.
Now, going back to what the OP wrote, it may be that the Hansons' plan would be significantly less intense and more specific than what the OP was previously doing (if he was doing weekly speed work at 5k pace and tempos at between HMP and MP). If that's the case, then the Hansons' plan would probably be a step in the right direction. And if your point is that the individual workouts that Hansons' prescribes are basically solid, marathon-specific workouts, then sure, I would go along with that. And I would assume, in general, that that's the strength of the plan and the main reason why the people who have success with Hansons' have the success they do.
Yeah....this is my basic thesis...not sure I have to address specific points, but I will point out that while you seem to have many issues with how the plan is structured, you're also aware that many people have success with the Hansons' plans, so maybe it's not the plan that needs reevaluation, it's how you judge/characterize/rate plans that should be reconsidered. "Yes, this has demonstrated to work, but it doesn't fit what in my head I think to be high priority for a marathon plan" kinda falls apart once you agree that it works (empirical vs. theoretical supporting arguments). But, we can discuss the basis of the merits the concepts, based as a guy who dropped 20 minutes from 3:2x to 3:0x in one Hanson's cycle, and read the book (so I could be wrong about the concepts but I have empirical support).
That being said, I do have issues with the way the workouts are set up. The first issue is the weekly structure. If one of the key points in your approach is the idea that "residual fatigue" will make it possible for three 16 mile "long runs" to prepare you for "the last 16 miles of your marathon," then why schedule two easy days leading up to the "long run"? Wouldn't it make more sense to do the tempo run and the long run back to back, with good recovery following that?
I think the "last 16 miles of the marathon" line is mostly bunk marketing talk or ad copy to get people to buy into a 16 mile long run instead of a 20+ mile long run. The real key for me of the "only 16 mile long run" was the fact that I was better prepared to hit a speed or strength workout 2 days after a long enough run and a decently long marathon pace workout 2 days after that. Your thinking seems a more traditional sense with a high point in the week followed by a couple of down days because you beat yourself up a bit. In my experience I could run more weekly mileage, more quality mileage, and more frequently given this structure. I think your approach sounds like you head to the edge of the well more frequently and back off, which was a finer line for me to walk.
Further, the long run is not the most important run of the week. It is equally important to the other workouts, and probably not even the hardest workout of the week. Thursday you're running 13-15 miles depending on what you pick for warm up and cool down with the bulk at marathon pace. Sunday you're running 16 miles where you (typically, assuming no possibly suggested modifications) don't really run faster than MP+30s, and can even go to the slow end of easy pacy (MP+2min) if you're not feeling up to it. Is that really the "pinnacle" workout for the week? There is no "pinnacle" workout it. You're just consistently getting in solid work, and recover, and then the next day you're ready for solid work again. If anything for me it felt like the 16 miler was like the "first 16 miles of the marathon", then 2 days later I'm working a pace just harder than comfortable to make mp more comfortable, then 2 days after that I'm doing the "last 10 miles of the marathon" on tiredish legs, then I get 2 days to 'recover' to start it over. Of course no workout is really like the "last x of the marathon" because if that were the case you'd need 2 weeks to recover. No single workout prepares you for the "last x of the marathon."
The second issue is the progression of the workouts. Basically, there isn't much.
What is the physiological advantage to progression for the sake of progression when compared to consistent good quality work? For example, is running 45-65 mpw over 10 weeks proven to be better for you than running 55mpw for 10 weeks? Or to make it even more complicated, lets consider the concept where going from 45-65 mpw puts you in a little bit of a hole by the end of it, but you can hit 58mpw indefinitely. Is progression really better just because it's progressing? Or is it better to get the work in while avoiding the hole?
From week 9 until the taper, you basically run the same 6 miles of MP-10 repeats and the same 8-10 mile MP tempo over and over. There is a progression of a kind from running 6 x 1 to 4 x 1.5 to 3 x 2 to 2 x 3, but then it cycles back down to 6 x 1 at the same pace. Maybe that makes sense in weeks 17, when you're in your taper, but why not continue the progression over the previous two weeks so that you run (say) 2 x 4 and 2 x 5, even if you need to slow down a notch to MP to hit that volume?
Why run a 2x5 marathon pace workout in the same week you're already running a 10 mile marathon pace run straight through? That feels like bumping up for the sake of bumping up, not because you can name a benefit. The taper is also pretty steep. From the second 3x2 workout week (which...when looking at the rests can be as hard as the 2x3 with 1mi rest) There are about 3 weeks left in the whole program. So in a traditional plan with a 3 week taper...would you really still be progressing your tempo runs 3 weeks out? or would you hold them the same or start reducing the intensity a little bit?
And why not include more variation in the tempo runs? If the athlete were to run MP+10 every other week, they should be able to run significantly more specific volume.
A big part of what Hanson's can do for an average to novice runner is help with your inherent sense of pace. By the time you get to the race, if you picked the right goal and followed the plan, your marathon pace becomes second nature. I'm not sure slowing down by 10s would get me that much more volume, but it would do a great job getting me comfortable running slower than goal pace. (thanks, i guess?)
What would I recommend? Well, remembering that the OP is a relatively inexperienced 21-year old who has kind of crashed and burned in his first two marathons, I think he would really benefit from building up his endurance base. As a first step, it should be relatively straightforward for the OP to build up to doing regular easy runs of about an hour. No particular pace, just easy. Specifically, easy enough that it feels natural to progressively run a little more. Maybe throw in a few strides or hill sprints every couple of days, maybe a little light fartlek, just to shake the legs out. From there, it should, again, be relatively straightforward to start go a little longer. Maybe something in the 1:20 - 1:40 range a couple of times a week, and a long run around two hours. Again, no particular pace, just easy (really easy if need be, maybe a little faster if it feels good). Keep doing a little easy speed, maybe experiment with doing really easy shakeout runs for doubles. Stick with that, and the OP's easy will probably get a little faster, while still being easy. As he gets stronger, when he's feeling good, some of his easy days can start to become progression runs, rhythm runs, tempo runs, what have you, and maybe his long runs can keep getting a little longer, or a little quicker (pick up toward the end, push on the hills, again, what have you). At this point, maybe he's running 50 miles a week (quite possibly more), with a long run of 2:00 (and possibly more), and some quicker running at a variety of paces - and he's doing it not at the peak of a training cycle, but as a base that he can build his training on for his next goal race (and his next training cycle after that).
This is a sound, patient, method to build a base and I would agree that being able to run 50mpw at the start of a cycle is better than at the end. It's good advice, but this also doesn't tell him him what he should do in a marathon specific training cycle. All you've done is tell him that he isn't properly building a base, which I agree with 100%
PS: Just to be clear, I am not anti-Hansons per se. I appreciate their contribution to the sport, and I'm happy to root for a number of their athletes (including Desi's super tough performance at Boston). Just not a fan of the training plans they put out for the general running public.
I will also say that for anyone already running 60mpw or more, the "advanced" plan as it's written above is a misnomer. They have additional online plans, a representative elite plan, and advice on how to increase the mileage for something in between "advanced" and "elite" in the book. I view the "advanced plan" as a great plan for someone who has run several marathons but done it the wrong way and no where near their potential, but it's not a truly advanced plan when compared to the most advanced plans available for Pfitzinger and Daniels. I've moved on from the "advanced" plan and I'm nowhere near an excellent runner. I think of it as the "everyman's advanced plan". Not the most advanced Hansons (or otherwise) plan available. It's a good book to get you started down the path of training for a marthon properly, it's simple, and it works. It's not the final finish line but an excellent stepping stone for someone like the OP.