I doubt that changing the icon would have much of an effect. The novelty of the crown has already worn off by this point for most players but the sort of player to pursue an icon just for the sake of having something 'unique' that not everybody has access to is going to pursue it no matter what the icon actually is.

I agree with some sort of mandatory synced test for key mechanics, though. Every combat mentor should, ideally, be familiar with concepts such as stack markers, knockbacks, 'look away' attacks and other common but key mechanics.