What about creating a repository for each "popular" package managers (apt, xbps, rpm, etc). And port the AUR packages to each repository, and kind of "chain" them in order to maintain all of them updated.
Example: I submit my own window manager to AUR, then a script detects there is a new package in the AUR, and creates a new package for another package manager.
I think that with this solution it will be easier to maintain and more reachable. Because it doesn't involves the creation of another package manager. Only the creation of "mirror" repositories of the AUR.
What do you guys think?