Well, can you also remove boosts from gear? Can you have negative boosts? Can you make sure the player can only apply a certain amount of boosts (like 1 or 2)? Can you have these changes done by an NPC merchant?

The last one is no, I haven't found a way to change the metadata via scripts (or Osiris) and it is a request for new feature here: http://larian.com/forums/ubbthreads.php?ubb=showflat&Number=633399

Please tell me if I am wrong, I would love to have more ways to change items.