Option to attack friendly champions instead of just recruiting them

I'd be in favour of being able to kill them if you also lost faction prestige as a result. Say their level / 2.

I think there are just generally too many of them around. It's bad for performance, they get in the way, and often I'll encounter a level 1 champion in the late game that I just don't want. Even if it's a light advantage I just don't want the macro. I'd like a system where the higher level ones didn't spawn until later in the game and unclaimed lower level ones disappeared after a while.

I don't want the ability to kill friendly champions and I don't think there are too many around.  I play on the higher levels and the AI usually beats me to them or kills them before I get them.  I usually only end up with 3 or 4.  I would like there to be a % chance of champions coming to us and offering their services like Master of Magic or Master of Orion.

I would have no use for it, but I don't see why others who want it couldn't select it as an option--provided, as was suggested, that some logical form of penalty was attached to attacking one naturally allied to your side.

Another benefit would be that factions with the betrayer ability would still be able to attack some champions of the opposing side if they wanted...

Sounds like a reasonable request. If you know you don't want them then the only alternative currently is letting the enemy (anyone else) have them. Makes sense for a third option to be added, such as "Assassinate", which could added besides Recruit and Rename and would take you to the tactical battle mode.
I don't see the need for a penalty unless you would get increased penalties in diplomacy from killing heroes from the opposite faction in addition to the ones already in place.

Great ideia.

Me too. Not only champions, but squads of units too. When the Knights of Asok come to you, they could offer to join your cause for money, otherwise they attack. It could be based on prestige...

Of any side, after all, they are betrayers.

I always plays as betrayers and natural leader so i can hire all champions and then steal their souls. This way i dont need to choose lots of magic traits at startup and get better traits at each level up.

If only they knew the fate in store for them...  And with Steal Soul (like other strategic spells), you don't even need to be next to the hero.  They agree to help you for nothing, so you repay them by stealing their souls.

Endorse. There are too many champions and an event-recruitment a la MoM would offset the limited numbers. I wish prestige would limit champion numbers also, as it is a fairly redundant factor currently.

I tried playing betrayers + free recruitment but I decided that because of the way EXP is split its not worth hiring all those champions. The 1 gildar wages are too burdensome. It would have been nice if I could kill all the heroes that didn't appeal to me so I could get extra experience. I wouldn't mind if its a betrayers only trait... it makes sense : D. 

I agree with the direction of the op.  My only concern would be if the A.I got a little too bloodthirsty and killed too many of the player aligned heroes.  An option to turn on MoM style random event hero recruitment would be pretty cool.