Amazing concept!
I also did this "At the start of the game, bunch of balanced blemmaye fight each other until you can afford some booster packs - after which you can go ham."
And on first pack got Siren and (forgot name) switch sides card. Game ending combo.
Maybe some kind of timer would help, ex incremental goals, need to reach Weight 10 before turn N, then reach Weight 20 before turn N*2 , etc
In any case, Great Innovative game, would love to talk about developing it further