Oh wow. Can't wait for this. If it's as solid as Mike's other tools it's going to be a winner. An interactive interface when doing blending would be so helpful.
For what it's worth Bill Blanshen has published a RGB Stars to NB combination script that seems to work really well. He uses a starless background of the RGB image so I wonder if he's using a similar approach.
Thanks, Adam. Exactly what I was looking for (and am actually in the middle of creating a starless HA version right now.) This should be a fun exploration and give me something to do during San Diego's annual June gloom.