I want to dump some of my Bcash coins stored in my paper wallet using trezor sweep function. I don't want to move the bitcoins stored on the same address. What risks am I taking? Only replay attacks?
That should really be the only risk. Although BCC says it is relay proof, there may still be problems with the way it functions as it's not as stable/secure as BTC.
I think there's something about exposing the private keys you're using but theoretically, there shouldn't be too much of a problem there as it's a hardware wallet so you're just exposing the private keys to a trezor wallet.