I wouldn't call Iron Will a villain in any way shape or form. All he did was teach Fluttershy to be assertive who promptly took it way too far. He didn't harm, threaten or bully anypony and genuinely thought he was helping ponies. Also he held up his deal of 100% satisfaction or its free without even trying to argue about it.
I don't disagree just I think he can be officially considered one. Also I think there was more then a little implied bullying from what he was teaching.
However your reasons are why I wouldn't mind seeing him again.