Hi there ! When playing the game i found out that those buff given to any recruited unit after owning specific building weren't retroactive. While not that much of a problem since the bonus are small, i would love a mechanic to give them to already recruited unit.
For my idea i will take for exemple what does another game named Heroe's Hour : when you unlock some feature for new recruited heroes, the one that are already recruited can benefit from those by going into the city that unlocked them. We could do exactly the same here : unit that haven't the bathouse or wargod buff can obtain them by going into owned cities that have them. It could also benefit summon that are spawned inside a city.
That's all for me, thanks for reading and have a nice day