In TOS, the helmsman (Sulu) would be the both the ship's pilot and the gunner.
The TOS navigator would also be the secondary gunner.
Ah yeah, I forgot to mention that to start with it's going to cover the TNG-DS9-VOY era. If it goes well I want to extend it back all the way to ENT, though.
Also, the same character can fill more than one role (like Worf and Tuvok being both Chief Tactical and Chief Security), but not if the role requires a separate console (like on the Galaxy class, there's no way Worf could've been both Tactical and Conn at the same time)