A model has the exact same restrictions here. fps doesn't drop because of the high amount of polygons, but due to this redrawing. This is the same for models. Gouraud shading won't smoothe the effect as the shape of the lightbeams totally depends on the texture used. But indeed, models are faster to render and so a better choice in this case. Yet they do not take away the limitations of the technique.
Thumb rule number one: prevent too much layers to overlap each other, e.g. only let the player view the effect from the side, never let him look into the beams.
About the 32bit colordepth, I didn't knew that. Thanks!