Interesting idea to add a levelling and research tree mechanic to this type of game!
I did worry when I was aiming for a 'build' that the options on the tree would water my build down, without the ability to pivot to a new build because of what seems like very limited ways to trim the deck.
Good stuff here! In games like these I'm a fan of cards having a 'type' meaning that other cards can interact with that type, not just specific cards.