This may not be a big issue, but I strongly think we need an option to attack heroes instead of just recruiting or leaving them there. There are several reasons for this:

1. If we don't want a specific hero, we either have to leave them for the enemy or to hire them and disband them, which seems silly

2. Even for our own side's heroes (empire or kingdom), we may not want them left for other sovereigns

3. It would provide for even more challenges / interesting battles as an option

If you feel it could be abused, then possible make it so that there is a reputation/influence hit if you attack heroes of your own side, but other than that, I think it makes a lot of sense!!!