I was thinking, why not throw in a time waster mini-game.
I have seen one game do this with a tiny texas holdem engine, and have players play for what would be gems in GA.
This would give players something to kill time on while they are waiting for those larger builds, marches and tech researches.
If the gambling connectation of texas holdem violates any liabilities or ToS, then simply switch the mini-game to one more appropriate.
Just an idea.