Just some quick thoughts:
1. As Peter suggests, deal with the arm as it is retracting. One way to do this is to put you hand on the jabbing shoulder and connect with the hand after its strike. You can also pop your attacker in the jaw from this position. Once you're made connection, see what kind of off balancing and technique you can do.
2. Why wait? You know you're being attacked, so why wait for the actual strike? Take the initiative, make uke block your strike, and use the block as the beginning of the technique.