Only leaders, really? It was an HQ Support units that I redeployed while under construction.
As far as I know you are able to redeploy: Supply wagons, balloons, signal companies, medical companies, HQ supports, engineers, and maybe pontoons, not 100% sure on those. You can also redeploy leaders with a divisional command if his division only contains one of the previous listed 'support' units (The best generals travel cross-country in stylish hot-air balloons.) I haven't tried it with more than one element though.
Sorry, I couldn't think of a better term than 'support' units. Maybe non-combat would have been better.