If your runner won't be convinced to bump up the mileage, then I recommend that they must be committed to doing a higher percentage of their runs at a quality pace, kind of like the British/Frank Horwill method. This is much harder than it sounds.
It's also going to be tough to fit in a decent long run on such low mileag. You may have to operate on a schedule of 1 long run every 10-14 days... Just my $.02
By the way, listen to what MPR has to say. He's coached me personally and I lowered my marathon by 23+ minutes with his guidance (high 2:40 range from 3:10+).
10 mile tempo question - I doubted this workout on paper, but I hit it 3 or 4 times in training, getting a little faster each time. If you're not overtraining, this workout is very achievable & a great confidence booster.
Structure question - I'll let MPR speak about this in more detail, but I know that we focused more on specific paces depending on the training phase [i.e., more MP stuff closer to the marathon]. He also structured a lot of my weeks to go from a certain pace range down or up to another pace range [i.e., fast intervals after a tempo run, etc.] There's always a reason for th structure, but the most important thing is to get out there and do the workout. Don't get too bogged down in the specifics.
Long Run - single most important thing for marathon training IMHO. We structured my long easy runs so that I didn't take any nutrition/fluids other than water. This had a side effect of training the body to burn its fuel sources more efficiently.