This. I really can't see why people keep saying that republics are bad, or that NR as the best form of republic. The volume of MP, (and the fact that it is focused on your preferred category) you get from short election cycles republics is borderline OP as it is, and given the events that fire at low RT, there's no real risk of becoming a monarchy unless you do something silly like mistiming a couple of diploannexations.
Ambrosinian in particular is downright ridiculous. Last time I played one, I couldn't actually spend all the MP I got.
I had this problem with Milan even without the republic government. It's the Milanese ideas combined with Imperial benefits (and some other choices I made).