Mistwell
Crusty Old Meatwad
I think the best "solution" for this supposed "problem" is the built-in role playing one. That is to say, summoned creatures summoned by a good aligned caster are good creatures. You killing them to get an extra hit onto a foe with an attack of opportunity is not a good act, but an evil act. Even summoned creatures feel pain, and I think it's fair to assume they do not want to be hit with a greatsword upside the head by the people who summon them.
Now with a malconvoker, I can understand it. But with a typical good aligned caster? Naw, I would start slamming your alignment left and right until you stopped or slid into an evil alignment, and that should take care of that.
And even a neutral character who is constantly slaying their own allied summoned creatures will eventually slide towards evil I think.
That's the way to deal with that silly, unrealistic and incredibly uncommon potential abuse of the system.
Now with a malconvoker, I can understand it. But with a typical good aligned caster? Naw, I would start slamming your alignment left and right until you stopped or slid into an evil alignment, and that should take care of that.
And even a neutral character who is constantly slaying their own allied summoned creatures will eventually slide towards evil I think.
That's the way to deal with that silly, unrealistic and incredibly uncommon potential abuse of the system.