It would probably be easier to step in and just to pay him a sum, granted he is a reasonable person and just upset with the model. A lot of times this type of situation can get out of hand. I helped a model in a similar situation, where the ex-manager/webmaster literally put a $10 million price tag on the domain just to be spiteful, but I got him down to about a grand. Still didn't think it was worth that much even, but it's sometimes easier to just pay up and move on.
If all else fails, register HIS name and make a trade!
