My headcanon is that at least temporary death is necessary to achieve Zoan awakening which would explain Kaido's weird hobby if he's not already awakened.
We know of at least one devil fruit that changed the appearance of it's user with Alvida so it could be argued that Boa's devil fruit possibly made her exceptionally beautiful.
I think we are reading too much into what gorosei should have/could have done. While there's no basis for this, I assume the fruit hasn't awakened since the void century. By the way they talk it doesn't seem like they have been in their positions since the void century so there must be many...