I do not know how to comment on this new SubD-in Nurbs .. excellent you are the best ..
Maybe when you have time it would be useful to be able to determine in the models imported before conversion which edges should be creased. a bit like it works with FreeShip. here is an old example below. this would allow you to create surfaces with sharp edges like a cube or something..
The ship is converted with edges creased and has a nice sharped nurbs surfaces..

Here the link to sources of Freeship..
https://github.com/markmal/freeship-plus-in-lazarus/releases