Something that I have always wanted was the ability to draw a mask using my mouse live on the output mix and be able to use this on a layer. Obviously this can be done with Photoshop in full screen on the projector but it would take into account any mix geometry and what not. Would save on lots of layers put together to creat a complex mask on the fly.

Possibly you could attach nodes to certain point and move those using General controllers?

(Just realised this was on another thread...) I still think it could be usefull feature for lots of theatrical shows.