Well, i begun playing SC just a few days ago, so i'll have to apply more to say something "good".
Now, just reading your ideas (all very smart), i thought that maybe IT should not "discount" unit prices, but boost MPP production of sites (+10%max for every advance, maybe), so there will be the choice to bombard enemy resources, or leave them untouched, hoping to grasp them intact. And maybe there should be an option to build less technological units, obviously at a lower price.. Germany and Italy later in the war certainly didn't built their best infantry army, instead fielded low experienced and aged troops, and (mainly italy) the "tech level" of these troops was for sure inferior to the one they had in the beginning of the war (shortage of equipment.. some divisions in late '43 were equipped with paper shoes). Maybe, instead of increasing Tanks' attack vs. infantry, they should have a chance to greatly decrease their supply (this is the true Blitzkrieg idea, not to crush the enemy, but to rush to his supply routes faster than his retreat speed), and maybe a chance (10-20%) to capture any army or corp badly injured or with low supply\readiness.. anyway, this game is fun.. but i found that concentration of forces, if in Europe (not using Massive Air Fleets) is difficult, in Africa is impossible..