Muse might be good.
Also, I think Moz would be great with a full orchestra. 'Lost' or 'Paris' and such would sound pretty gear.
I suppose view is dependant on which direction one would like to see him progress. G23 suggests Mountain Goats (who are f***ing great). On the few tracks I listened to they were quite sparse and urgent. More like The Smith's. So one can take the position that he needs to take stepback.
For myself I see him getting grander and lush. His music luxuriating in his voice.
Its a testament to 'Himself' that as an artist he keeps both sides interested.
The Mountain Goats. I think Darnielle and co would approach the situation with respect, good songs in mind, and steer M toward a simpler yet more fitting sound. And probably tell him straight up if something stinks. Which is the most important thing for anyone to potentially work with him.
"Sit down, shut up, and try harder. You're Morrissey."
But with the current state of things in recent years, he's rapidly and widely become known more as a punchline than a musician of merit.
I’ll choose two. Being a fanboy of both I’d still love to see him collaborate with Bernard butler. Taking his work with the tears as a cue he still has a classic British guitar sound and that albums cinematic grandness in spots would go really well with modern morrissey. I like to think what home is a ? Would sound like with Bernard behind it. My acne choice would be Patrick wolf who’s music is very eclectic. in spots and very uniquely modern electro and in others very classical often mixed together in the same song and always theatrical
The reality is that most of these would be better than his current band. I'd probably give top choice to Radiohead and The National. I'd love to hear Morrissey's voice over some of Radiohead's atmospheric and haunting music.