If you are a Sage you stay a sage, if you are a shadow, you stay a shadow. If you want to roll a Jedi Knight ( different class ) then roll a Jedi Knight. Jedi Consular is a class, in that class there is Sage and Shadow, once you have chosen your path, its the path you have to stay with. Now within each you have talents, you can have those talents reset and redo the talents within the adv class you have chosen.