Basics:
An ability to have a saver node in the render materials such that I can render out jus a specularity pass or special pass I create. I.e Like in Digial Fusion.
A frame viewer which I could save one individual frame out if I wanted to in any format I chose.
Particles and Voxels. I would love the ability to map a displacement to a set of 3D particles. I know anything is possible with taron-kung fu programming!
An interactive render where I can adjust lighting in real-time, kind of like what pixar has been using for a while and Fprime does very well.