I'd use crouch for the holding-trigger, so you can still use tools while hanging.
If you did that, then maybe even some builders could find some use for this.
Hanging is a toggle, you click once and then as long as you hold the RMB you'll stay there, until you either click again, release the RMB or use the wall again (to climb on).
Is it possible to vault over things?
Not particularly, it's more or less exactly as written. Although I was thinking of looking at rky's slide playertype and seeing about implementing that code so you slide when crouching and holding the RMB. Baseball slide. :V