Erm... Maximillian's advisors aren't telling him to do it, he wanted to do it himself. Stupid on his part, but nonetheless that was one of his objectives.
And the Empire gets its arms from France, of course. That was Maximillian's original plan, and it would have happened if the Republicans didn't have as much military strength to occupy Maximillian's forces.
And actually, France can't make it's own gatling guns. IIRC France's equivalent was the militareuse, a contraption that required each barrel to be loaded individually and was part of the reason they got completely destroyed in the Franco-Prussian war. Not just because it was ineffective, but because French artillery commanders apparently replaced too much for their regular cannon with it.
