This is a little out there and could be considered cannon, BUT!
What about bounty hunters? But instead of everyone fighting over boba fett, becuase I know thats what people would do. Design new bounty hunters based on the star wars universe. I mean, there is a Bounty Hunter's Guild. I just got done reading the first book about it. Why not make that the third "race"?
I mean extensive research and design would be needed, but it would be a cool middleground between the Rebel and Imperial struggle.
When fighting Imps, make it a deal gone wrong.
And when fighting Rebs, make it a commission from the empire.
I'd gladly donate time and effort into helping designing new characters.