The delegations cannot cause a tx to revert, nor does a tx revert cause the delegations to revert. So there is no need to send 7702 txs without calldata.
This isn’t to say that determining if a delegation was successful is fool proof, because since delegations don’t cause tx reverts, their inclusion in a block isn’t a testament to their validity. That needs to be determined separately or the RPC can return the outcome.
I think doing so at the RPC is reasonable. Clients can compute the result of the delegations on the fly fairly cheaply so it seems fair to lump into some of the other computations we already do.