You could put thinner, lighter tires on your 700c wheels... I just put some 700x32's on a wheel that had been running 700x23's for 6 months in order to handle the local potholes and unpaved paths/river trail, and I noticed the HUGE difference in inertia (in the opposite direction). I may go back to the 23's when the road crew has had time to patch up all the winter potholes, but by then I'll want the 32's to deal with the snow.

The design of the rim is more of an issue than it's nominal diameter. If I RELIED on my bike, I don't think I'd have a problem with a little extra rotational inertia if it built a stronger wheel.