About Nahobino/SMT V protag, I was mostly joking but I don't think it's that difficult to happen.
I mean, it's unlikely and I still believe Demi-fiend is a more likely option if we get a SMT rep. But I wouldn't count out Nahobino for CP11 even if his game comes out at the end of the year.
Consider that
- Sakurai and Atlus have already worked closely (Joker), and both sides seem to have a nice relationship as it was shown here
- SMT V is, as we know, an important Switch exclusive (announced at the very first Switch presentation btw). So it's not out of the question Nintendo would keep a DLC spot for SMT V. Both Nintendo and Atlus have been pushing the game quite a lot, with the game being the first simultaneous worldwide release in Atlus' history, which probably was thanks to Nintendo
- Joker and the content he brought was only Persona content, not even a Jack Frost costume or spirit, when he's basically Atlus' mascot. So there wouldn't be overlap of content
- Fighter Pass 2 was officially announced in September 2019, though reliable people such as Imran Khan stated the deals were finalized around E3 2019. At that point we already knew about SMT V and it's protagonist.
- This could be a similar situation to Byleth's, where Sakurai played an early build of the game. Maybe not exactly the same here, but he and Atlus could be regularly in touch so Sakurai is aware of the details of SMT V and Nahobino.
- Assuming it happens, other content wouldn't be really a problem. The stage could be the desert looking place we have seen multiple times, probably the first area of the game. Music selection would have songs from previous SMT games and of course, V. And spirits would probably be iconic demons from the whole series, not specific characters from SMT V.
- The hardest part would be the moveset IMO, but not that hard if you ask me. No matter who they choose I'm pretty convinced any SMT protag would have some demon summoning as part of the moveset. If it would be manual summoning, or just demons appearing when the character does certain moves, I don't know. Jack Frost and Pixie would be there for sure and maybe 2-3 more demons.
As for Nahobino himself, I feel that going by his design alone would be enough for Sakurai to be creative. But in this scenario he would probably be in touch with Atlus a lot, so they would give him a lot of info about what Nahobino can do, and his abilities, so I don't think it's impossible.
I feel there's enough margin for SMT V protag to be the final fighter, obviously that's up to Nintendo and if they feel like pushing the game even more. It would be hard to pull off for them? Yeah, but not impossible. If Atlus and Sakurai are in frequent contact and all which would be the case if they did this... It could happen, it's not that crazy if you ask me.