Casinos could allow players to swap two assets from their own pool of coins because they are receiving deposits in various coins. But honestly, I don't see this becoming a thing in the future as it doesn't generate any profit for the platforms and they aren't running non-profitable organizations after all.
Not to mention that casinos would have to maintain liquidity in different cryptocurrencies, which would certainly entail more operational efforts and an even bigger bankroll. Another issue is that they would be exposed to market volatility with different crypto assets, which is certainly not a part of their core business.
Some casino has internal exchange system available. AmoreJaz has made a
list here. I think it won't create much impact in the bankroll of a casino if the players use the internal exchange service. Because the player doesn't exchange a fixed coin always. Moreover, the exchange service aren't used to escape the high withdrawal fee only. If a user exchange from ‘X’ coin to ‘Y’ coin then they do the vice versa also.
Gambling sites charge high fee (1%-5%) for the coin exchange as well. If a real exchange site can maintain profit by taking 0.1% to 0.5% fee then why a casino will loss their bankroll by charging higher fee! Market volatility won't create much impact in the bankroll management as the crypto gambling sites charge high fee for the exchange.
BTW, you haven't said anything about these websites. What have you thought about them?
Don't forget to recheck our old suggestions:
Owl.games,
Thunderpick. Also give a look at
Livecasino. They are operated by the same team of Bitcasino/Sportsbet. Livecasino min withdrawal amount is 0.0005 BTC. And they don't charge any withdrawal fee as well.