According to the old Decipher CCG, TIE fighters at the battle of Endor had been upgraded with maneuvering thrusters.
To provide some customizability for the basic TIE fighter, create a TIE Fighter only modification that adds one Evade die. Making it cost three or four points would be fine because it' would make them too expensive to swarm up per se.
At three points Iit would invalidate SD, but on TIE fighters only. Alternatively, they could make it cost four to be a bit safer.