I'd rate it the same damage as either a club or a staff, and if you wanted to do non-standard things with them, I'd make them Stunts. What do you perceive to be the advantages of a three-section staff?
You may also be looking for a lot more rules crunch than DFRPG is intended to provide. Optimizing weapon choice is for systems like D&D: DFRPG is primarily about narrative flavor. There is still some number crunching to do, of course.
I wasn't looking for crunch so much, as suggestions for stunts that would let me take advantage of a versatile weapon. I've thought of things like using declarations to pass certain kinds of defenses when used as a flail, and using it to justify disarming manoeuvres with Redirected Force but that's all I have.
Weapon 2, with an aspect of THREE-SECTION STAFF. Styles and grips fuel Declarations with the Martial Artist stunt.
If a player asked to have a specially-well-made staff that was weapon 3, I'd say yes.
So a weapon can have an aspect? I assume it would just work like one of my ordinary aspects, with the same rules for invocation and compels?