Eventually, that would be a good idea, but not right now. There aren't really enough of those crusaders to make such a challenge interesting. Of the top of my head, I can only think of 10 crusaders that fall within those categories, which is just barely enough for a full formation, which means there would be nearly no differentiation between formations between players, which is half the fun of challenges.

But again, I'm not saying this isn't a good idea. Just a bit early for the idea to be applied.