Maybe it wouldn't fit the lore that well about powering up that 'one' weapon but c'mon..
With the removal of the dual spec and we can now play 'whatever' spec we want, we are even more limited than we were before because of AP.
Imo, if you have 200k AP, you should be able to spend 200k AP in all specs.
I've read things about people quitting the game because their guild wanted them to play another spec but they didn't have enough AP for that spec so they got benched. You could say 'find another guild' or whatever but we shouldn't be so limited with this system.
/rant