So he gets revenge on you for getting revenge on him and then the player gets revenge for Kellog's revenge as revenge for the player's initial revenge?
You do realise that if you need to put *spoiler* in the title then the thread should have been started in the Spoiler Forum?
Any hoo, this would be a pretty good scenario for DLC and maybe have him think that he's still with his wife so that he kidnaps someone's child thinking it's Mary and you have to track him down.
Edit: This'd also re-enforce people's opinion that Synths are dangerous and shouldn't be allowed to run around free.