Good Stuff thus far..I'd like to point out as well, if you look at coach's such as Harry Wilson(Ovett Coach) and Jimmy Hedley(cramm coach), you'll notice that both spend what I would consider an extended period of time building there base. 20-24 weeks of basebuilding, with smooth transitions into vo2 max/LT training. However, Wilson believed never to neglect speed, and had his athletes do some sort of short speed work after Long runs, other "medium-effort" runs.
Now on the other hand, You have the kenyans who spend about 3-5 months worth doing base training, but at a considerably faster pace. Though, from what I read, they don't focus so much on "hammering" track intervals, yet they seem to put more emphasis on Lactate threshold. For example, Noah Ngeny during his off peak season had a schedule of:
Monday: Am 90 min. Pm 40 min easy
Tuesday: Fartlek 3 min hard, 1 min easy for 40 min (10 min buildup)
Wednesday: 40 min building to almost 10k race pace PM 50-60 easy
Thursday: 1 hr "steady" run
Friday: 30 min. at "high speed" Pm. 45 min easy
Saturday: Long "tempo" run through hilly route.
Note though, this is only one portion of the whole picture. Here I think for 800m/1500m runners that running XC is important because it not only toughens the mind mentally, it gives you that extra bit of strength and endurance. So perhaps, in the base training phase, you could begin with 2 months of building a solid base, nothing out of the norm, just your basic doubles and 1x tempo. Then once you start progressing into the 12-20 week period, you start integrating 4-5 tempo runs per week (3-4 if your tired etc. etc.) along with 1 hill session. My thoughts are, Americans are hammering away sessions, but don't have the building blocks to support them a whole season. Notice, if you re-read, most of these runners have had a 3-5 month base. As of late the typical base period lasts maybe 2-3 months. I think Americans have it backwards in that they feel they need to hammer sessions first, and put the aerobic capacity aside. Perhaps bite the bullet, and put in a good 3/4 month base so you enable yourself to run "fast" for extended periods of time (tempo/LT), then as mentioned previous, work on what takes the shortest time to develop: SPEED!