The Family Heirloom has no current use apart from cosmetic purposes. In legacy, the heirloom increased your tradition slider so if in the case of imminent death you'd retain extra stats (had your tradition slider not been all the way). An idea that can be implemented is an ancestral bonus. The ancestral bonus would allow you to get extra numen points if you are wearing the CRAFTED family heirloom of your most recent ancestor. I don't recall how many numen points you acquire per turn in at the moment, in legacy, it was 3 numen points full traditional slider. Now with the ancestral bonus of the family heirloom, you'd have a chance to acquire extra points. On top of the 3 numen points, you may have a percent chance of getting an extra 1-5 points.
This is just an idea that came to me when I was watching Jorbo's live stream. I'm open to comments and opinions about this idea.