These are really cool John.
I started my Patreon with the idea of making variations too. My first map was like that, but somewhere on the way I have lost motivation to do them.
As you said they are quite a challange and it is not a quicky, despite the fact that the actual map may depict small area, making all the variations are very time consuming.

I still have few maps to finish like that too. Gotta go back to it soon.