So first off I want to mention that Nintendo has made a pretty surprising announcement that Jet Force Gemini, a rather underrated third person shooter made by Rare for the N64, is coming to NSO, with Japan getting it November 30 and the rest of the world getting it in December. I recommend playing this as I loved this game back in my teens. Hopefully this indicates more Rare games coming soon too (I'm still surprised Banjo-Tooie isn't on the service yet, but we also really need Diddy Kong Racing and DK64).
But an interesting thing to go along with this is Nintendo has confirmed that for NSO in Japan they're going to be releasing a separate NSO app meant for games rated for "adults," as in that country both Jet Force Gemini (named "Star Twins" in Japan) and Goldeneye have the Japanese equivalent of the M rating, dubbed "Z" (Japan is far more strict regarding violence, as even though JFG doesn't feature human blood and gore, the simple fact it still has lots of green alien blood and gore is enough to get it Japan's highest age rating).
IMO this is something I feel NSO needs in all regions as I really want Nintendo to start adding games that have an ESRB M rating or PEGI 16 and 18+ ratings to the service. For example if we're gonna see more Rare games then this separate app would be perfect for Conker's Bad Fur Day and Perfect Dark, but this would also be good for games like classic Mortal Kombat (like put the Genesis version of MK1 but then the SNES ports of MK2 and 3 could be added as Nintendo didn't censor the SNES ports of those two), the N64 Duke Nukem games (Duke 64 was a unique port of Duke 3D, and the N64 got an exclusive third person Duke game called "Zero Hour"), and some of the N64's more forgotten M rated games like Forsaken (a cyberpunk Descent-like) and the N64 port of Nightmare Creatures.