I used all custom ones for my campaign. If we had continued playing, I was considering doing a revamp. I wouldn’t say any were too powerful (compared to the core ones), but some were just kind of bad. There’s definitely an art to it. However, the easiest thing to do is MacGuyver a new ancestry out of existing feats. I don’t think that would be too problematic. (It also lets you make sure no one has darkvision. Yay!)My only real complaint with PF2e is to some extent it lives and dies by Ancestries and Archetypes, and I'm not at all confident of keeping the balance present when doing my own.