The Maule is the true "work horse" for most of the Hawaii jobs. The Maule is where you can really rack up some flying time (cargo, live cargo, medical flights, passenger flights and clandestine cargo). I think it's a must have airplane, though a working EGT would sure help.
I would imagine that the 1.2 million sq miles being thrown around for Alaska is not one DLC. It's more likely that it's multiple DLCs. Each DLC for the "Journey to Alaska" would probably use the same model for Hawaii DLC (includes one aircraft) - Alaska actually could include quite a bit of DLC if it was piece mealed out. All that beautiful scenery just screams Track IR.