Are there any services around, providing wallets for BTC, ETC and other currencies which can be used by gambling site to deposit/withdraw/exchange crypto from users, without actually implementing connection to crypto network?
No? I'm not entirely sure what you're asking but I'll assume that you're looking for wallets which directly connect to casinos without making users deposit/withdraw their crypto from the casino through conventional means. If that's accurate, then the only wallets that casinos use are primarily the ones that they run on their website. If you want to move the crypto into/out of the casino, you'll have to use the network normally.
That could be an interesting business plan, to be honest. You'd need to do a lot of networking and get casino owners on board, but a "bank" for casino funds which lets users deposit and withdraw without leaving history on the network could have some value. Of course, then you'd have centralization issues...