Given the cards that are coming out, it might be nice if there were some towers that had benefits for two or three elements, rather than the totally random quantum towers. Pretty basic, but what I was thinking was something like this:
Gravimetric Tower
When GT comes into play, gain 1 earth and 1 aether quanta
GT produces 1 gravity quanta during your turn
Upgraded versions of the tower might produce 2 random quanta per turn from the 3 types it's associated with; for balance, it wouldn't produce quanta when it comes into play.
There would have to be a lot of them to represent all the possible combinations -- but that could wait: for the time being, 12+ of them would be a good start.