I think this would be a good change. It's stupid to meaninglessly copy from one race to the next. I want at least a little thought put into "Does this make sense." Boobs on a lizard are glaringly nonsensical
Like being warm-blooded?
Dragonborn are monotremes. They'll be keeping mammary glands, but have no nipples, like other momotremes, in my campaign.
They'll have a cloaca, and hold eggs internally for most of the gestation period.