Caps on Traps: tie it to League, not TH
Let the number of traps you place be based on your league rather than town hall. (If you go down a league you can keep the traps you have set, but can't place any more than what your new (lower) cap would be).
I don't know how important this upgrade would be- but I have noticed players with >2100 cups like traps and want more, and players under that just want enough to keep their resources safe.
furthermore, it is a way (albeit a minor way) to make cups matter a little more in the game.