A quantum upkeep sounds logical, but it's untested in the actual game except for flooding, which is hardly ever used; thus the effects on balance haven't been really explored.
If 1 quantum isn't enough, an alternate idea is one quantum upkeep per creature; thus there's no upkeep if you're not using the quint, but if you're going devtal you'd better be prepared. Admittedly, that looks and sounds a bit clunky, but I'm just throwing it out there. We don't want to deviate too far form the norm, I think.