I'm note sure I understood. So you deposit in BTC, and when you enter a game, let's say roulette, or a poker table etc, you convert your BTC to the in game currency. You keep that rate stable and when you exit that game, you convert the in game currency back to BTC at the same rate?
Yes. It's done only to have more or less stable minimal bet and bet increment values. Like a bitcoin payments in dollar casino, but without currency conversion tricks.
I think it's a good idea, and I actually saw something similar in poker houses that have multi currency tables. Their balance account is converted to that table currency and when they leave, are converted back, exactly at the same rate used when they entered the room. I don't see any problem in doing something like that with BTC.