Let me give you two scenarios and let me know how your casino would do in those situations.

Scenario 1:
Date: 1 July 2019
Deposited: 0.5 bitcoin at 10k EUR/btc exchange rate
Converted value at my bankroll: 5k EUR
 
Date: 3 July 2019
Winning from games: 500 EUR
Current bankroll value: 5500 EUR
Bitcoin market price: 12k EUR
Converted to btc while withdrawing: 0.4583 btc

So in this scenario, I will be getting less numbers of bitcoin even after winning 500 EUR from the games. How do you handle this??

Now Scenario 2:
Date: 1 July 2019
Deposited: 0.5 bitcoin at 10k EUR/btc exchange rate
Converted value at my bankroll: 5k EUR
 
Date: 3 July 2019
Loss from games: 500 EUR
Current bankroll value: 4500 EUR
Bitcoin market price: 8k EUR
Converted to btc while withdrawing: 0.5625 btc

In this scenario, I am making losses but getting more bitcoins while withdrawing.

Please let me know how do you propose to handle such situations? I think it is wise to implement crypto wallets instead of converting cryptos to fiat. You will be significantly exposed in exchange rate fluctuation risk.