I'd settle for Home on Jam missiles, and a line in the drone targeting protocols that says, "If enemy jammer detected within sight, range, and accuracy of weapons, focus fire but record and stay away from it". So if you have an ECM unit, the drones will keep out of its bubble where possible. If you take that jammer unit and hide it in Heavy Woods, the drones will not fire on it (except for Mortar and artillery). If the to-hit for going after your jammer is 13 or higher, the drones will not open fire on it.
So if you activate the ECM on an equipped unit, expect the enemy drones to try to shred it. If they are missile armed, expect to see lots of missiles using your jammer as a targeting guide. Of course, if you sit in the cluster of Light Woods, expect to see lots of HoJ missiles blowing up on the trees around you (making sure to keep the to-hit for the HoJas close to 12 as possible, without going over). This results in the drones only using their missile systems against you, ignoring other Mechs in your force.
Hmm, I'll have to rethink the order protocol. Maybe something along the lines if it is 4 pts easier to hit another unit, or if it took fire, the drone will target the other unit before the jammer. This could get complex.