For the weapon exploit:
Both Magma Blade and Ground Dash work (and it's actually easier to alternate between them). If you have Ultimate Buster, you actually have a choice between 6 weapons (all except Yammar Option and Meteor Rain) since they all apply the same concept: reducing any vertical velocity X currently has to 0 so that once he starts moving, he gets more distance per drop.
For charged sabers (either Blade or Shadow):
I just tried it out, but you can only use a charged saber ONCE in midair. The only exception is when you use a charged saber -> Giga Attack -> charged saber combo (much like in X2 where you could air dash -> Speed Burner -> air dash). Until you touch the floor/wall/ladder/rope, you can only use your buster.
I'm not sure if getting hit resets this, but it's highly unlikely and useless anyways, outside of fights. I believe charged specials also don't reset, but I have to try it out to confirm.
UPDATE:
[youtube]http://www.youtube.com/watch?v=fvNv2E9k6Ic[/youtube]
Here it is for reference. I would've tested Jumper a bit more, but they all ended in failure and I don't feel the need to repeat the results again and again, due to time restraints. Also, I did have more recordings, but they were iffy so I chose not to include them.