He's the new genetic master for the Stormtroopers... Yeah I know original trilogy Stormtroopers aren't Clonetroopers... but clearly there is some kind of inter-trooper war going on. New clones vs conscripts?
Actually, I'm not all that sure that the "new" Stormtroooers are conscripts. If you remember, before R2 and C3PO ruined his life, Luke wanted to go to the Imperial Academy.