Stuck as Ravenna in Patch 1.0.10 – How to Deal with Naples and Tuscany?

Hi everyone,
I’m looking for some advice on how to continue my campaign in patch 1.0.10, as I’m currently stuck in this situation.

As the Signoria of Ravenna, I have occupied and annexed the northern part of Italy. The Duchy of Tuscany, which extends down to Rome, is a subject of Naples and is currently being annexed.

This is where the problem arises: I can’t declare war on Naples because it has far more troops than I do, and Hungary would also join the war, since they share the same queen. My allies are France and England, but they are almost constantly at war, which makes it difficult to rely on them to start a conflict.

Do you have any suggestions on how to proceed?
I’ve also tried using “Agitate for Liberty” on Tuscany, but it didn’t have much effect (partly because I’m not entirely sure how it works), and Tuscany is still being annexed by Naples, with very high loyalty.