I would love to see the lineage comeback. I think there's a place for it in the pony profiles, they just haven't implemented it yet.
In V1, I took screen shots of my ponies as foals, adults, and traited adults, along with all their statistics. I then made a screen-cap log of the pony's birth certificate, parents/grandparents, brothers & sisters, and offspring. My secondary account was a breeding experiment for Neon-Green Colored Ponies, and I was even making a family tree for my starter pony. Since the lineage is no longer available, I've not been taking screenshots lately, I'm also not doing a lot of breeding.