I played your scenario last night, and it was pretty fun. A few suggestions though:
1) You may want to give the Hero units +1 or +2 hit points. They're pretty strong as is, but I was still able to wipe out the Fellowship (with the exception of Aragon) losing only a few easily replaceable Uruk-hai.
2) You may want to make it so Isengard can't build things like knights, pikemen, swordsmen, etc. Why should I build a swordsman when I can build an Orc that is better and cheaper? Same with knights and warg riders.
3) I'm with Yoda in that you need to rename the wonders and techs. You don't need to use all of the wonders, so you can cut the ones you don't need out of the loop. Likewise, you don't need all of the techs, so cut out the ones you don't need by setting them to Era: None. You'll probably have to make up a lot of stuff with regards to wonders. For example, you can change Sun Tzu's Academy to something like Sauron's Army or Call of the Dark Lord, or something else like that.
4) You should probably give Isengard a few standard starting structures, like a temple and marketplace, etc in addition to the walls and barracks.
5) Are Militia supposed to have a movement rate of 2? Just wondering if that was intentional.
6) To solve the problem with unit support costs, you could just uncheck the Requires Support box for some of the units, such as the Uruk-hai for example. If you do this, though, you should probably increase their cost.
If I think of anything else, I'll post it here. All in all, it was a fun scenario to play.