I didn’t really design it to do that - when you remove all but the billboards or impostors it removes all the mesh data apart from a plane, but when you remove LOD0 and keep a reduced version, it retains the full vertex data but stores the reduction value.
However it doesn’t look like it would be too hard to implement something like that, I’m working on an update for rdLODtools atm anyway so I’ll see if I can add it for the update.