Well, if you want to be a roleplayer, you are not limited to the powers you do in the AT trays.
Your most important powers as a roleplayer are the ones that
aren't listed in your AT trays!
For example, I knew of several psychics who roleplayed Fortunas, Controllers, Dominators. They had the power to read minds when talking to other roleplayers. So they indicated on their biography card something like this:
"Natalia Fairweather has the power to sense thoughts."
So, when playing, she might give out a signal via /tell:
[[I'm reading your mind right now. What are you thinking?]]
And good roleplayers who are messaged this way (and you
do want to be a good roleplayer, don't you?) will be obliged to play along:
[[I'm thinking of the revenge I am plotting against Femme Fencer.]]
See how important those powers which are listed on your biography card can be? Those powers--the powers you roleplay with--are, in many ways, much more important than the powers you use to fight off NPCs.
So my first bit of advice to you is to figure out this character's roleplay powers
before figuring out the primary and secondary builds. Is this character truly 'deathless' insofar as he or she can...say...rise from the dead, if killed during a text fight? Or can this character survive tremendous physical punishment, even a thermonuclear bomb blast? Or does this character's connection to this "dream world" give him or her the power to place another character in a dream world? Can this character move between the dream world and the real world at will? Or after receiving a trauma?
Those are the questions I would ask when designing a new roleplay character. If I can figure out the character's roleplaying powers, the rest of the build just falls into place.