I could throw them on a character just for funsies and see what greater rift I could get to. The only thing stopping me is the futility of it, but if there were a leaderboard for it, it wouldn't be for nothing, and tons of other people would get a whole new gearing metagame out of it as well. It'd be so much fun to see what people come up with. And how high people could get, I wouldn't care if 1st place was 20 gr's below the normal leaderboards - it'd be its own league, apples and oranges. Maybe by the season's end the boards would be dominated by one build the way certain set builds do now, but it'd be a lot of fun to see it grow, and to see where my idea of a build falls out in the beginning, and how I can tweak it to come back ahead of the competition.
I'd participate for sure. Would you? When everyone hits their own GR wall with the cookie-cutter builds, it'd give them something else to do while just hoping to upgrade non-ancient set pieces to ancients - so I don't think I'm alone.