Hello Assassins,
Personally I haven't played Assassin's Creed Unity yet, and as it seems an "Era" template in Ben Franklin's wikia says he appears in Unity, but nothing else is mention in the page, whether he truly appears or not... Since I'm not sure, I leave it to the hands of yous, and do note that if the case is that he's only mentioned in Unity (not seen) then do at least write that.
"We work in the dark to serve the light, then we return to the dark."
-Adieu!