SmegInThePants

Fantasy General soundtrack = my fav

both good ideas, 1) hard cap (let player choose x, where x is the limit), 2) the stick (penalty for too many of one type, in cost or effectiveness or both, let player choose X where X is when the penalty begins to apply). X should perhaps be a percentage rather than a hard number, so that it auto-scales w/fleet size/map size. Another, third option would be the carrot: 3) combined arms bonuses. 3.5) or perhaps a d&d style 'favored enemy' choice in the tech tree (you get to pick 1 sp