First and. Foremost I really enjoyed the concepts of the half-elf and half-orc in the playtest, especially once they became heritages instead of a regular ancestry feat.
Something I think would be really cool to have in 2e would be something like that for more races instead of mostly environmental variants. This way we could have some similar ancestry feats attached to them.
The example my playgroup discussed most would be for the goblin ancestry. You could make a Half-orc-like heritage feat, but since it’s for goblins, you become a bugbear instead, to emphasize the increased size and strength, and provide proficiencies for iconic bugbear weapons. How cool would a Giant Totem Bugbear Barbarian be? Or throw everyone for a loop with a bugbear bard? Or for a more half elf type you could be a hobgoblin, emphasizing grace and dexterity. As the game grows you could keep tying races to these variants and add similar feats, but with the appropriate racial flavors. The possibility is probably one of the things I would be most excited to see and explore if done well.