I don't disagree that it could be possible to create really powerful Exotic Weapons, plus make unique masteries for them to make them even more powerful... I just don't see anyone at WotC who might be willing to do that as part of 5E24 design. Because at the end of the day... really uniquely-designed and powerful Exotic Weapons + masteries just become an alternative equivalent to Magic Weapons, don't they?
Nothing wrong with the idea per se... but is there enough of an audience for them to warrant WotC to design them (rather than a 3PP making a system for players to grab off of DMsG)?