Y'all want a plan for what we'll do if Mathilde? I'll give y'all a plan for what we'll do if Mathilde gets caught!
Kick the problem upstairs.
The thing to keep in mind is that this? This is all legal. Mathilde has broken no laws of the Imperium and have kept to both the letter and the spirit of the articles. This is quite possibly the least legally ambigious vote we've had in the thread's history! You can even see this in the arguments that people use. The vote is neck and neck enough that if there was a finger to point at Truth legally speaking, the Faith faction would hammer it like a Sigmarite hammers orc skulls.
The worst case scenario of Mathilde getting caught is that it would cause the cults to declare a "war" on the colleges, right? Well, that sort of scenario is exactly why we have the articles in the first place! The social contract states that the various magic users swear to serve the Empire faithfully and loyally for their entire life, with no legal possibility of backing out or leaving, and in return the Empire protects the wizards from zealous lunatics attacking them because their chosen lord or lady in the sky tells them to! The Empire, as an institution, is duty-bound to take our side and protect the people that we care about.
Most cults aren't going to mess with that. Oh, they'll complain and they'll move in the shadows of plausible deniability, but openly acting against the Empire is a step too far. Or rather, if they were willing to act against certifiably loyal servants of the Empire because an entity who doesn't even pay taxes says so, it's probably best that we figure that out now and not in the middle of a crisis like a Storm of Chaos.
And if the Empire doesn't support us? If they abandon their oaths and leave our people to hang and dry? Then we evacuate the colleges to the Karak-8-Peaks. Belegar would never abandon us, not without some serious oathbreaking on our part, and the people who live there are already (somewhat) used to the presence of Wizards. It'll be rough, and we won't be able to save everybody, but we can with indeed carve out a new place for human magic-users to live and be as safe as magic-users can get in the Warhammer universe. And this time, it'll be in a country that actually appreciates what we can do for them.