Theloss is only for building Land Units though and thus completely alright in my opinion. You should look at other types of buildings to increase land unit
as once you move on to a Leather Factory the type of units you build no longer need the Tannery.
Alternatively the bonus to Land Unitfrom Tannery could be faded away slowly when units no longer needing as much leather are starting to be built. By the time of Leather Factory that
bonus should be gone already.
Cheers
There's two separate bonuses from the Tannery:
- +15% production for Land Units
- +5% general production with each of Salt and Wax
I will agree that the hammer penalty that is showing up is probably the total penalty in all cases, but I don't think you should be penalized for upgrading a building.