I'm trying out Boxer right now. So far I'm liking it, although it doesn't have the bumper jump like bumper jumper. I probably will just stick to Slayer Pro Bumper Jumper and not worrying about having to use holding AAs... B to crouch was a major turn-off for me on Default. Same goes for stick down to sprint. I would really like to have 5 triggers/bumpers (shoot, grenade, pummel, AA, Jump) but sadly that can't happen. Perhaps a setup with grenade throw on the face could work.
If there was an option that switched ONLY the crouch and run (nothing else, AT ALL), I'd have been happy. I hate pressing the analog stick to run - I'm used to having to press something completely unattached to my "walk" button to run in my many other games. Combining their button, separated only by pressure, is highly annoying. I too would have preferred to keep the crouch where run is now. It's much more useful, especially when able to toggle. Using it for running brings about breaks in overall motion for me.
It works for me because I use jet pack more often than not. So something like Bumper Jumper I just couldn't use because of not being able to jet pack and aim at the same time. I don't find that I need to crouch and aim at the same time, I'll use it when someone's come around a corner or something to me not when we're charging at each other.