I don't see anything wrong with adding a quiz show at the end. This IS supposed to be the spiritual successor to the Banjo games, so why not include one? If it's too on the nose, then that goes for pretty much everything this game represents. It IS the spiritual successor, therefore this is one of the best nods to the Banjo series I can think of, world logic be damned. Even if the big bad is an evil scientist, or some kind of war general, or a demon from the 7th level of Hell, there's no reason why he/she can't do a quiz show. It's a cartoony game, there's barely any logic to begin with! And you know if they do it, it's going to be hilarious, which is all the more reason to do it!
As for a twist ending, well... I'm sure there's going to be a "collect all the things" objective to get a 2nd ending, as in basically all past Rare games, but as for a twist tacked onto the regular ending, I don't really have a problem with that. In fact, I kind of love it when I find out there's a lot more to the game than I originally thought. It's like, "What? You thought the game was over? NOPE! In fact, now you gotta explore a level in HELL! Good luck collecting all the things, WIMP!" Kind of like the end to Super Mario 3D World.