Who cares if the casual fans didn't recognize Shelby? I doubt they recognized Janeway before Caretaker? I would've enjoyed seeing a series centered on Shelby, all while laughing that she made captain before Riker.
I could see her being rather hard on the Maquis, which could lead to some interesting friction, which was supposed to be there all along anyways. It would be a great character arc for her to instantly distrust these these terrorists, but slowly become to rely upon them.
As for the Borg? At least she'd have a reason to want to take on the Borg so often, and when she came up with a technobabble solution of the week to beat them at least we wouldn't be muttering bs so loudly. Though I don't see her siding with the Borg over 8472 at all. More like the other way around.