I think I am going to go against the flow here and say no to your wife fighting the Ex. It is a sexy idea worthy of fantasy, foreplay, and pollfights, but way too many landmines in that field to make it a reality. There is a reason the ex is the ex. She is fighting to get back in the picture and unless you want her in the picture say no. You might say she is out of the picture as soon as they fight, but she is already back in the picture if they fight. It would be different if they both wanted to fight each other to settle the score (maybe the wife stole you from the ex, maybe they always hated each other, maybe they fought before but not to a conclusion), or if they were fighting over you while you were dating. But you already picked and married your champion. What you really have to ask is what is the worst case senario? As I see it, they fight, ex wins, wife divorces you and takes you to the cleaners for having your ex beat her up, and then you remember why the ex is the ex and you end up alone. If your wife is willing to fight you are the luckiest man on the planet and I hate you!!! Find somebody else for her to fight without all the extra-curricular emotional entanglements. You'll both be much happier in the long run I think.