I don't know where you people get the name "Lightstaff." I really don't. Starwars.com, Star Wars RPG, KOTOR, KOTOR2, etc. They all use the same name for it, the true name, Double-Bladed Lightsaber.
A "lightstaff" is impossible, because, Staves are blunt-end weapons. A lightsaber cuts, because it projects a high-concentration blade-like laser (of restricted size -- somehow).
A Staff would denote a weapon that can be handled anywhere upon the entirety of the weapon, that can be used in a combat method. I use the staff sometimes, and they're not really used the same way Darth Maul used his Double-Bladed Lightsaber anyway. (Although, they can be used to block arrows and the such... Speaking of which, you should be really careful about doing such a thing...)