1. They should release a heavily locked-down version of Android, which manufacturers and carriers cannot modify - apart from basics like bundled apps, widgets and wallpapers (uninstallable). Update would come direct from Google, and hardware support would be limited to specific components.

2. Make all of Android closed source and shut down AOSP. What is the point of it anyway?

This would solve the fragmentation problem, and be better for consumers since they would get updates quicker and for a longer time. Paradoxically it would lead to less 'choice' for consumers.