The chainline argument never quite made sense to me since to get to the middle of the total gear range, where presumably you're spending most of your time, you're going to be somewhat cross-chained. Of course, the tradeoff of the reversed setup is that your lowest and highest gears might be unusable, but you can likely work around that.
Seat/chainstay clearance is of course the big problem, and you can't easily do anything about that.