Once you have heavies, armor, engine, and guns what do you get? Maybe Biodeisel incase someone gets nukes, or absorbant incase someone gets rails. Basically you research stuff you don't need because someone requests it or you might need it someday. I suggest research at the end of each tree that give tanks or infantry passive benifits, or improved versions of junk you already have, or useful abilities. They would be moderately priced, but take a long time. There would not be superweapons, or game enders, just something worth researching after heavies (or mediums) and weapons are done. The research could be boring, like + cannon damage, or it could be interesting, like giving all tanks a turbo button. The goal would be to give teams something useful to research later in the game, without adding more tiers of weapons and tanks. Teams that could afford to keep research going would have an advantage. The benifits should not be enough that a team would want to rush them, or skip weapons or tanks to get, but it should also be things that are useful in any situation. Ideally the benifits should help make mediums viable, so that a team with tricked out upgraded mediums could hold their ground against heavies (until the heavies got upgrades too). For example: Researching Upgraded Chassis would be the prereq for High Strength Alloys, which increase the weight limit and hull health of all tanks. After UML and HE are researched in the chem tree, High Yeild warheads could be researched, giving all cannons and missiles a larger splash and extra damage. Sorry about how vague everything is, I know the research tree is going to be overhauled sooner or later so I didn't bother with anything specific. I just think this would be a good way to make the later game a little less monotonous and keep research and the radar relevant.