We played an unbound army yesterday at the tournament and I felt we had the advantage as it was an objectives mission. If you have a bound army with lots of troops vs an unbound army in an objectives mission you are in a good spot.
The reason I bring this up is that I know many folks want to disallow the unbound right out of the box but perhaps an alternative is to allow unbound and have your missions be objective based. My prediction would be that the amount of unbound armies would not be that great once people realized it limited your chance to win.