Interestingly now it seems Kate could be in a similar situation for the show. If she comes back it could cause problems for the OC.
Which is why I don't expect a recast Kate to ever show, not unless they physically disable her so she can't be a vigilante again, at which point it just adds insult to injury.
IMO it was odd enough that Kate had use of Wayne Tower without any mention of inheritance (seemed accepted outside of just Luke since she let Martha's necklace get used for an exhibit), an OC doing it just seems bizarre.
And I hate the lack of explanation about characters such as Alfred and Robin, they provide enough information to let us know they exist, then ignore it (by implication Alfred is alive, going by Julia's remark). Oh well.
[Edit] Oh, just remembered something - how is this for a plot hole: In COIE the Monitor said Kate was the "Bat of the Future". Guess he didn't know what he was talking about.