The real issue with Smiths 2020 is probably not who plays the guitar, nor it's political.
Smiths 2020 would be suicidal for Morrissey.
He managed to build a stable band with people who are otherwise sessionist musicians who can perfectly work for other artists or bands. They are loyal to him, but their loyalty is certainly backed up by a salary (which is obvious, none of them is probably rich enough as to work for free). I don't think Morrissey can tell them "give me a year, I will be having fun with my old pals... I'll phone you when I'm done... explore life as a homeless in the meanwhile!".
His other option would be to pay them without giving them work during the "Smiths adventure"... but The Smiths involves dividing the earnings a 25% between 4 persons. Rourke and Joyce won't work without their 25%.
And the future of The Smiths would always be fragile if they actually united... a new album would be a bit weird, a tour can't last forever (unless you are into the Sisters of Mercy, who managed to keep their promotion tour of Vision Thing since 1990!)... And they don't even get along very well, so it's not easy to work together.
So it would be suicidal, even if he wanted to... and probably he doesn't want to!
Reality on the guitar!!!