WarKirby
Arty person
There's also no easy way to reduce their gold cost without also decreasing their hammer cost.
Yes there is.
Remove the inbuilt "upgrade" ability into a settler, and instead create an "Upgrade to settler" spell which subtracts an amount of gold you specifiy.
I'm pretty sure the doviello do it. I'm vertain it's possible for spells to have a gold cost (Pelemoc stuff, etc) and I'm also certain it's possible for a spell to transform a unit (lichdom)
So what is missing? Seems like nothing.
although it's slightly messy, codewise, I don't see anything stopping you from setting the price of a settler upgrade independantly from all the others, using this kind of method. Am I wrong?