The warrior career book would be pretty close to the top of my list, followed by seeker and/or sentinel.
For species or alternate ways of knowing the force, the Dathomir could be fun, plus ya know... Night Sisters. I wouldn't mind seeing a return to the Hapes Cluster or the Tapani Sector, but when it comes to species, honestly I feel it's not too difficult to adjust the starting characteristics, take away some of the starting XP and give them a flavorful racial ability or a boost die to subset of skills. Also, I am pretty sure I'm one of a few people who wouldn't want to see a return of the Noghri, though really if you get rid of their racial martial art I might stand down from my "Noghri starts with No for a reason" platform.
Other than that... A Juyo/Vapaad form could be fun, but rolling my force rating to activate Forsee tells me if it's a thing, it will be in the warrior book. It makes sense to go there, but it means they would have one fewer spec tree to try and round out warrior into something a little more than pilots with chips on their shoulders the size of a small moon.
