As you said, 'bronze [working]', not copper, is all Dog Soldiers need. Which means: DO NOT trade him horse for any reason.Hopefully he does not have horse or bronze and is literally incapable of plotting war right now.
Dog Soldier + Chariot would be enough to start plotting with just horse I think since Dog Soldier is his axe replacement.
Are you saying he can't plot war without another attack unit like Chariot? I didn't know that. What if he had a spear?
@MG, glad you tested. I was not aware that this fist icon would not appear. Seems like it was planned by the mapmaker.