I already made a tread about SEV going beserk, you should read it. What about Boss going force sensitive with the ability to see 1s into the future like the Jedi. Then you could add the story that Boss saw SEV alive somewhere, lets say, Mannan.
OR general Grievous tried to clone his own trooper to infiltrate the Republic and he needed SEV for the perfect infiltrator.
Then again I'm just force sensitive