Ha. The Empire, arent they fun. I simply join them, and then become the next emperor. Lots of gifting required, but makes life easy on me.
Austria kept being a dickwad over the fact that Milan and Tyrol were my vassals (I was Naples and had JUST joined the Empire). Well, as much as I did not like Austria, fighting an Austrian Emperor as Naples is not very fun. Over a series of 3-4 wars fought down to the man. (Ran out of manpower each time and had to give up) I had to abandon Tyrol. Another 2 wars later, I almost had to abandon Milan...Until I became the emperor. Had about 1000 manpower left when this happen, then infinite manpower changed the tide immensely. Roflstomped Austria right after. As I finished up, Bohemia declared on Austria because they felt like it. I answered the call to protect the Empire state from BS when I let Bohemian army head down to Gurz or somewhat.
Safe to say, in less than 2 years I had broken down the 2 most powerful empire states. Silly gooses.
TL;DR: Become Emperor Asap. Much luls happen.