I think its great to develop both official and ”non-official” supplements. I run a Six Seasons- based campaign and have a very ”political” group of players and wanted some intrigue and powerplay among the Haraborn. So I created some bloodlines based on the ”founding fathers” of the clan so that different coalitions and loyalties would be logical. I also distributed the NPCs and steads among the different bloodlines.
But I would never publish anything of this without the consent of Andrew Logan Montgomery who was created and written the books about the Haraborn. But the bloodlines exists at ”my” gaming table.