It wouldn't be what I would do, but then again I'm a former lawyer with many friends who are lawyers. But if the best OP can do is get some preliminary advice from Hacker News, it's worth giving it a shot.
What would you suggest OP do instead of asking HN?
If I were a former lawyer, I wouldn't give any advice other than general knowledge.
e.g.
"Could you sue on behalf of the shareholders of your CEO's embezzlement and win? Maybe? Should you? I don't know, I'm not your attorney, and I haven't studied any of your claims."
Our intention is not to recover the 13 weeks of pay, but we would rather let them keep it, and remove them from the company being that's the "pay out" they get for their shares.
Although, we are trying to understand if this could be considered as fraud so we can remove them with a legally solid reason, and confiscate their shares.
That's terrible advice.