I've said it before, but I think it is even more relevant now as we approach the launch of the XBox SX.
MS is already a big time 3rd party publisher on the Switch, arguably the most successful because of Minecraft, but other games like Cuphead and Ori have done well also. Banjo is in Smash obviously.
We know from market research that a big majority of Switch owners also buy one of the XBox or Playstation as a stationary home console ... if you're Microsoft you should want the huge Nintendo fan base (Switch is on pace to sell 100+ million) to lean towards XBox.
IPs like Halo and Forza could clean up on the Switch with *older* franchise entries and even stuff like Killer Instinct would be very popular. Make these IP popular with Nintendo fans (get Master Chief in Smash Bros. while you're at it) and when it comes time for Switch owners to buy one of the big box home consoles, they will be more predisposed to an XBox if they become fans of things like Halo and Forza and Killer Instinct and Battletoads.
Doesn't mean new Halo or Forza games have to be on Switch, they likely wouldn't run well anyway, but older Halo and Forza games and Killer Instinct, Rare Replay ... why not? The old way of thinking it outdated, MS would not be hurt at all with back catalog titles be available on Switch, they would only stand to benefit.
MS needs to start thinking outside of the box, if they can become a staple for Nintendo fans as the top non-Nintendo publisher on Switch, when a Switch fan who loves Halo is choosing a new console he/she is more apt to choose the system that has the newest Halo game. Or even a service, lots of Nintendo fans could get hooked on MS IP and then decide they want to subscribe to xCloud. The Nintendo audience is huge, 10-20 million Switch extra owners also buying an XBox SX or subbing to xCloud would be big for Microsoft. Whatever MS can do to change the metrics of being so behind Sony they should do.
