Cool idea
Here's my suggestions:
Remove the trader as a scout and create a new scout unit called "Handlinger", perhaps let it change forms between human and wolf.
I feel the cactacae need some more thought, they seem a little underpowered to me. I remember in Perdido Street Station it says somewhere that cactacae are almost immune to missiles and piercing-type weapons (which is why they invented the Rivebow) but with your current implementation of 3 protection they'd get creamed up by arrow fire.
I'm not sure about giving nature to biothaumaturgs, after all new crobuzon doesnt give a crap about Nature, look at how polluted new crobuzon is, and blood magic pretty much covers all aspects of their remaking. I'd suggest giving biothaumaturgs 1 construction 1 blood, and the remakers 2 construction 1 nature. The Scar has references to thaumaturgs animating constructs in the battle against amarda, so they are definitely very strong in construction magic.