Phoenix-
Concerning playing as a Cerulean, I would personally suggest you spend time developing your darker and lighter sides as a normal member of society. This way, you can get a better feel for your character, develop the "Akalak thingy" to your desires, and play with when/how your other side comes out. Cerulean, as mentioned in their
lore page, are named by the Council and their faces tattooed so all Akalak are aware of their status. It is something I would suggest that if you want to delve into you develop through roleplay (and by all means I'm here to help with each step!).
You mentioned that you don't want to take your darker half too far, but in order to be classified as a Cerulean you will have to prove to the Council (or they will have to make the assumption) that it is your darker side that motivates your actions. Once "sentenced" to the Cerulean, there's no turning back, so it is a decision not to take lightly. Of course, Ceruleans are a required part of Akalak society and Riverfall will have uses for them.
Anyway, think about it some, keep roleplaying your character and see what fits best for you or the direction you want to take it. If you want ideas or want to run ideas by me, go ahead and send me a PM and we'll see what we can do!