Yes, I have seen the video of your system before too. Good work.
How have you implemented it, one quad and rotate all the time or only when swapping image. Does cpu rotate your quads and changes textures/texture offset or gpu?
In any case, one problem that would be nice to be solved is the 'popping' that happens on image change and impostor to mesh change.
For the first case, I was thinking if I were to change the image using cpu, I could do the change when the quad is outside of camera view. It has its disadvantages, but its not a bad idea.
Thou atm I do the updates on the gpu, thus all I can think of is some sort of blending depending on the viewing angle.