This might be a hot take, and since I obviously can't play one yet I might not fully understand what they do but:
I don't like the idea of needing to rely on another whole dragon to boost stats of hatchlings. It's a cool idea but doesn't entirely make sense. Why would one species of dragon need to rely on another just to have stronger offspring? My current understanding is that some of the better stats can't be obtained without it.
Instead, I think it could make more sense for the BW to just help with incubation times, egg spawning times, and those kinds of factors. Heck maybe even make it so you could lay additional eggs. But I don't think it should influence the stats at all.