tyCache Sprite display option

[moonjam]

I'm working on some scenes with a lot of tyCached particles and wondered if it would be possible to get something like the Sprite display mode as a preview option? The current options for viewport optimisation are all fantastic but I find myself missing the fast visual feedback from Sprites when previewing animations for grain like simulations. Alternatively, if that's a pain, something like the mesh override that permits proxy geometry but only in the viewport would be brilliant.