So will it feature a real-time action battle system, since it's no longer a single player experience? I don't know how you'll be able to incorporate that smoothly.

If you want my advice, I'd go for something that looks similar to FF6, but doesn't actually feature any of the exact same graphics, characters, or worlds. That way, you can have custom player worlds, and expand every now and then to give it a real-time feel that you wouldn't get using someone else's world that plays out in its own fashion. That would get boring.