Remember that
zigzag tape for glider planes?
I was wondering if putting something similar to that around the edge of the rim would do anything productive. Maybe it would create enough turbulence that the spokes could slice through the air more easily. You couldn't run rim brakes on it, but drums drag less anyway.
As far as the wheel design, I'm just thinking out loud at this point, but maybe something like this, but with spaces between the rings:
That way, maybe air would flow across it from the front, but side winds wouldn't catch it as much as a solid disc.