"It is the CAA who issue the licence (and a CAA AME who issues the medical). So the court case (whether class action or by individual) would have to be heard first so you could have a valid licence to keep flying!"
Regarding the change of the ops manual I see no problem, as you wait to start flying "after 60" till you have a won.
Regarding just continue to fly and challenge possible future consequences in court, I doubt that the CAA would revoke someone's licence before the case has gained legal force if the outcome is unclear. If you win, you have done nothing wrong and no revokation can be done. If the licence was revoked before you won, you might be eligible for damage.
Just continuing to fly commercial single pilot ops after the age of 60 sure is risky. Unfortunately, I believe it is the easiest way to try the case. If you just fly once and without passengers and still making it an official commercial single pilot ops, the consequences should be less harsh if you don't gain any success. I believe details regarding how to challenge the legislation should be stated by someone that knows the law in the applicable jurisdiction, as this is very different between individual EC countries.