I know what you meant. But what you're selling isn't fact.
Personally, I don't think opening the occassional Public World when none are available is going to do much damage to the current publics. I do like the "only two available at once" idea, maybe I'd make it three in case of two duds, but I do see problems with that as mentioned. Couple those two ideas and I think the "problem" is solved in a matter of weeks.