I think this would be a good idea but there are "tanks" that don't even want to generate enmity and only play as PLD / WAR because they want to wield a sword or an axe.

But most times you only see them in the first few dungeons anyway, natural selection will take care of them I guess. ^^
Yet I've been in Cutter's Cry with a tank that didn't use any enmity generating ability ...

Still leveling some classes I'm more worried about having to trust level 40 - 50 tanks wearing level 10 DoM accessories though.