I don't think leads should necessarily have the ability to be un-kickable. Just the leader and co-leader(s) that you can trust. If your leader and have 2-3 co-leaders are un-kickable you should be ok if somebody decides to get stupid and kick everybody out. At least 1 of them should be able to come on and re-recruit everybody that was lost.
You don't want a situation where a newer lead is causing a problem and other leads are on but cant do anything because the only one that could kick the problematic lead is the leader themselves.
This would go hand in hand with my thread about more command levels in a guild,and being able to give rec powers with lesser ranked leads.