I suggest that each engine type and each armor type have 2 versions, regular and upgraded. The regular version would be a bit worse than the current versions, and the upgraded version would be a bit better than the current version. The upgraded version would be research-able after the regular version (one branch deeper in the research tree). I'm suggesting this because it would be VERY easy to implement(editing text files) and would add variety and playability to the game. Pros: Increased playability/variety More tools to help balance game play with Cons: Might not get balanced well Might be perceived as "busy work" for the commander P.S. I'm guessing MetalSmith has already done this many times on his own.