I do hope if our characters are still going to be confronting their personal issues, it'd be a little less, eh... 'stage play' about it, I guess? Conceptually, P4 (and by extension, P2) had a great idea going by literally facing your other self, but I don't think it could ever escape a kind of clumsiness in how those confrontations wound up playing out and resolving.
On the topic of demons and negotiations, I wouldn't miss either, but wouldn't recoil at either. I actually like the Shadows, at least, the idea of them. It's really cool how Persona represents the Jungian dynamic and Shadows contribute more to the vibe that Persona has been going for, I think, especially as of late. Demons add another supernatural layer to the story that I'm not convinced has to be there. I do think that Shadows really need to escape the confines of 'table with mask on it' and 'evil Hulk Hogan', though.
And while other games have Law/Order/Neutral, I'm just not seeing any reason why it has to be there at all. If it's about giving the side characters more personal stake in what's happening in the primary narrative, there's less obtuse ways of achieving that than integrating the whole three domain thing. I'm just struggling to see why it'd be worth the potential effort.