I'd be ok for a content sharing deal that was weighed in Nintendo's favor.
Like MS gets ports of certain older Wii U titles and some Nintendo Virtual Console classics -- so maybe like a 4K port of Super Mario 3D World, Xenoblade X, Twilight Princess, etc. But no Breath of the Wild, no Mario Odyessy, etc. etc.
In exchange, Nintendo gets Microsoft support like Minecraft crossovers, Halo Collection port for Switch, Killer Instinct, Rare games on Virtual Console, and maybe a chance to work with Rare again (Banjo-Kazooie for Switch for instance).
But why should Nintendo be the one going third party, there's a very good chance IMO that Switch outsells the XBox One in the end. It's eventually going to drop in price and have Pokemon and the portable Nintendo market that comes with it.
