I'd really like to see someone build a deflex riser with a fast cam system.
I'm guessing that this isn't likely to happen. The parallel limb craze seems to be driving the reflex designs to even greater extremes. To make a parallel limb design with a reflex riser would leave you with an enormous brace height. Not likely to get 320 fps out of something like that. Of course, maybe they've got a design with 6" limbs that might work.