We don't know for sure, all we have to go on in a casting call sheet, and they often use fake names to cover up the identity of characters from the comics, so even though the name doesn't come from the comics, that doesn't mean the character isn't from the comics. There's already at least one theory floating around about who she might be.
I've heard two -- Holly Robinson (ally of Catwoman) and Harper Row (Bluebird).
Is this going to be the first superhero comic book TV series where the lead character is not the same character as in the comic?
Well,
Agents of SHIELD, sort of, since the lead of the SHIELD comics it's credited as being based on was Nick Fury.
Batman Beyond comes close, since Terry McGinnis was a "Batman" with no precedent in the comics; though Bruce Wayne was still a lead character, so it's borderline. And you could quibble whether
The Incredible Hulk's "Dr. David Banner, physician, scientist" is the same character as Dr. Robert Bruce Banner, nuclear physicist.
Outside of superhero comics, there's
iZombie, whose lead on TV was Liv Moore instead of Gwen Dylan. The
Timecop series replaced the comics' Max Walker with Jack Logan.
And simply swapping out actors isn't going to have any knock-on effects either?
Not where the writing is concerned. The same storylines can continue as before, just performed differently.
You're going to end up with more or less a different character anyway.
A different interpretation of the character's personality, but with the same backstory, relationships, and unresolved conflicts. Hardly a complete break like a new character would be.
People are going to feel cheated anyway due to Rose's departure. Having her replacement keep the Kate Kane name isn't going to prevent that.
I wouldn't feel cheated if she were recast with an equally engaging actress. For instance, if they'd taken up Jade Tailor on her offer to take over playing Kate, I would've been delighted.