That is true, I was just saying based on the obvious (eye color). But yeah, they could definitely be candidates. Vexen had the whole replica program and, like you said, Xemnas valued him to some extent. You could even say Xaldin was doing his own "experiments" on Beast, he had his own case study going on there. I could definitely see them being/staying on the bad side. They are also numbers 3 and 4.
It doesn't seem like Aeleus or Ienzo would go bad again, and I hope they don't I really like them and REALLY want to see more of them.
Kind of straying into a new topic, do you think the fact that Ienzo was an orphan or his parents will have any significance in the future? I feel like the probability is low but it's just a thought. I haven't seen any comments or theories on that yet by anyone. Or I'm just blatantly missing these things lol