Not a terrible idea initially, blend in with farm equipment, excellent off road capability, small and nimble. However there's a reason Geneva conventions require military personnel and equipment to be distinct from civilians.
Do you want all your civilian farmers blown up? Because this is how you do that.
I though the only distinction was for medical vehicles and military vehicles. There is a whole class of vehicles called Technical which is pretty much a pickup with a heavy machine gun mounted to it.
https://en.m.wikipedia.org/wiki/Technical_(vehicle)
Reminds me of this old Eastern Bloc joke (read it in a thick slavic accent):
Pravda reports imperialist forces unjustly and underhandedly attacked peaceful farm tractors of great USSR doing peaceful harvesting work. Our brave farmers returned fire and flew back to USSR territory.