So does Bustadice, for example. If I want to have my coins immediately I can check "Instant withdrawal" and the withdrawal request will be processed immediately, but with the corresponding fees. If I don't need the coins immediately, the withdrawal takes up to 24 hours, so the requests will be paid out in a batch processing I think.
The fees are quite different for the 2 variants. Currently, for example, on Bustadice the instant withdraw costs 324 bits, the slower one 62 bits.
Yes,,, I think more and more sites are implementing this now and I think everyone should accept that batch transactions save everyone more money and more time.
I think casinos should just explore the option of batch payment and charge people a "temporary sum" of fees. But then, once processing the batch payments, they then divide the actual fee used to pay among all withdrawals, return the balance as part of the withdrawal or to the account (user can choose).