if the the uchiha can do iznagi with a three tome sharingan no strings attached like we saw tobi and danzo with their sharingans then we muist ask the question why didnt the uchiha try and gank bang hasihrama during his hay day to kill him. So what if they lose their eye sight they lost many in their time of war.
If you need great skill what skill are we talking about exactly? MS? So far MS doesnt seem to be needed.
There difinitly som,ething going on no matter which way you look at it.
This would either result in major plot hole or quite simply theres more to it than we know.