One of the things I really liked about my 595 was the status leds on each channel. Not only useful for simple troubleshooting, they also made it have a sort of 'looking into the matrix' feel. I could look down at the board in the garage and know what portion of the sequence was playing.
I'm not sure if this is possible, but I think it would be neat if you could somehow marry the DMX frontend common to the Lynx family, with some PWM drivers, like LedTriks. Basically a board that would sit just past the USB->DMX device working as a 2way splitter (like the 4 channel one currently available). One leg goes out to all the devices, the other uses a start channel of 1, and has 512 leds. I don't think the leds would be able to support the full range of 256 for the dim value. I would imagine the pic would have to reduce the resolution to something a little more manageable, since the led's are already in a matrix. I think even 8 or 16 levels of dim would be enough to make something like this usable.
Way past my current knowledge to design, but whatcha guys think?