pixpot Theoretically? Everything is possible. In reality, however, it would likely be a gigantic change to make; not for the faint of heart.
The reason why you have to unlock Owner before using other profile after a reboot is being Owner houses config options and settings that other profiles use. You can't keep Owner at rest while using other profiles, so you have to do the first unlock after a reboot to get it out of the "Before First Unlock" state.
Changing that would be fundamentally changing how user profiles work at their core and would be a gigantic change to port to other Android versions in the future. Like I said, theoretically possible, practically impossible.