id rather see Kara than Cassandra [not really a fan of her]. not sure how much of a connection youd want Kara to have with Nightwing or anyone else for that matter, as it is pretty much stated earlier in the RP, Supes, is his sort of mentor now that hes out of the bats shadow, coming to him in troubled times, etc. of course getting the alias of Nightwing from him.