Thanks for the head start on this!
I had to make some tweaks to get this to deal with nested leafs and frames as we use them and I imagine I'll need to work with it more to do some things we typically do with our door numbers (e.g., if a room only has one door we don't append a letter) but it worked well in a little test project I made.
Now, however, the first Python node is throwing an error;
It was working 5 minutes ago... all I did was copy the walls/doors/etc. to a clean file and restart everything.
Also, I don't know if it's related but earlier I was having trouble with Get Family Instance By Category node. It was returning an Empty List. It worked fine in a blank definition however.
For anybody else working with nested families I've include my modified definition to get you started.