Growing throughout a match

[Humate]

I dont mind having a temp upgrade system, provided everything else is worked out.
Also a tech-tree system is pretty cool too. Ive been playing hearthstone, and duel of champions experimenting with building decks, and I enjoy that to an extent. On the flipside, for fps I dont believe players should be too dependent on such things, but the system itself should be potent enough for players not to simply ignore it (like in etqw).