This is a really clever idea, but eventually it felt like the amount of money I made was totally dependent on the order I draw my cards. Sometimes I'd be stuck with nothing but high cards and forced to watch each tower dwindle away. I also wish there was a way I could queue-up cards to be played after the one I already placed, but every time I tried it, the new card took priority over the old one and I missed my chance.
But like I said, it's a very cool mechanic and I think with some tuning it could become really addictive and engaging!