Originally posted by knighttemplar1960:

Raids are based on which boss(es) have been defeated in that world and not on who participated in that defeat. The boss kill is world based not player based.

I think the OP is aware that this is how it currently works. They're suggesting a different method.
Without being able to dig into the source code ourselves, it's impossible to know if it can be done without a major overhaul. Sometimes these things are simple, and sometimes they're very impractical.
I personally think it's a good idea. Let's let the developers decide if it's possible or not.