One of my players has come up with an idea for a weapon which is entirely new as far as I know. He wants a scythe which, with a push of a button/twist of the handle, has the blade extend up and straighten, so it becomes a polearm. The idea being that with Exotic weapon Prof and this weapon, he can use a swift action when he gets charged to suddenly become braced for the charge with the weapon.
We've figured that he'd need Exotic Weapon Proficiency, and that anyone trying to sunder the weapon would get +2 to the roll, due to the semi-collapsible nature of the haft. Also, I should stress that this is for a BBEG NPC in a campaign he's planning, not for a PC, so it's likely not going to totally unbalance the campaign or anything, just looking for ideas as to what damage/crit multipliers it'd have, and want to know if anyone has any ideas to make it cooler....