Vexen / Even

So TECHNICALLY this is the Even model, but unlike certain other KH characters I could name (looking at YOU Xaldin >.>) there's really no functional difference between the two.

I'll probably end up doing Repliku next (I refuse to refer to him as Dark Riku, he's just a time displaced Repliku) but after that... I dunno.

I'm trying to come up with my own Organization XIII mix, since I don't like duplicates and I'm not splitting up either the Days or BBS trio on the light side either. That leaves either Organization short at least 2 members. I also could not be more indifferent to Young Xehanort (I have the main Xehanort/Ansem/Xemnas trio, kiddie pool Xehanort holds 0 interest) so that leaves 3 slots from True Org XIII to fill in with OG Org members.

Vexen was an easy add (he's arguably more relevant to both organizations than most recurring members are, given the prevalence of the Replica program) but I'm stuck on who to give slots to between Demyx, Lexaeus, Xaldin, and Zexion.