Matt asked if I was suggesting this as an add on to Chord Builder, which provoked one idea.
I think it would make a lot of sense to incorporate such progression tool into Song menu. While I don't personally use BIAB for cover songs, sometimes I would open a pre-made song to learn how it was constructed.

Ideally this progression tool can be done such way, so user can optionally "connect" it to existing BIAB song library and it would populate a list of songs that share / based on progression you choose.