no you can t cheat to change you side on the fly ..... you can change your binds and the configuration of the force powers but the effects won t show up until you respawn.....
and byt he way you can add something to the script :
open jk2mp.cfg and check the force powers settings
seta forcepowers "6-1-330100000030000333"
this is the list of all your forcepowers .....
so configure it for light side,quit the game
and add in
set light_side "seta forcepowers 6-1-330100000030000333;......."
and do the same thing for dark side.
so you don t have to configure you forcpowers eachtime you change side with the menu.
the only problem is if the force mastery level changes you'll have to change your configs ....