Hmmm. I actually think most of Emerald would be decent as knights. Like you, I considered apping Itachi as a knight but thought it would be more interesting to give him the support of a team because that's not really something he seemed to have in canon. But he probably would be pretty good at it. And most of the members of the team have independent streaks that would make them workable as knights, I think

I'm not sure of the second team, though, maybe TE? Or Citrine. It's hard to say since I don't follow all the teams that closely. Iolite is pretty independent so they could theoretically be knights, I guess, except I think a lot of them would be terrifying. Hibari and Vincent as knights? sob it would be terrible.

Also as to the knights becoming colored teams I can't speak for all of them but I know Sasuke would hate it. He kind of hates the team concept. It'd be awful for him. XD

Do you have any plans you want to do with Raven?