An OS design issue: File types associated with their appropriate programs

Hey guys, sup? Refresh your design skills, cause you're gonna need 'em here.

I know this is a pure SO question, but I thought I should ask here as well, providing the crosslinks, no effort will get lost. The SO guys seem to shy away when they see a Unity3D tag for some reason lol - I really need as much help I could gather, I also think the problem is interesting which is another reason why I shared it.

Any help is greatly appreciated. Thanks.