If they do an FPS game, I highly doubt it would tie into other Nintendo games. It would probably be more Geist style, meaning it would be mostly single player action with some "gimmick" to make it stand out. It would be more focused and small scale than what you are talking about, focusing mostly on great level design and interesting weapons moreso than things like destructible environments and vehicles.
The multiplayer would be fairly standard, with more focus on the "gimmick" and an objective based scoring system as opposed to a kill based scoring system.
That is how I see it at least, but even that is unlikely...







