"seeking your valuable advise, here."
Thank you for the compliment!
"What's preventing current shareholders from forming a class action lawsuit against our loyal government if everything goes south for us?"
That depends on what the cause of action is. Derivative lawsuits are prevented by HERA. Therefore, private damages would need to occur. Furthermore, HERA would prevent an injunction. Only money damages are available.
Lawsuits already exist that meet these needs. A class action is unnecessary, since the damages for most shareholders is not very much. Most shareholders bought after the crash and so wouldnt be able to sue for much.
The lawsuits that already exist meet our needs.
Though I wouldnt mind seeing a few lawsuits challenging HERA as unconstitutional. The problem would be standing, as most dont have it since most bought their shares after HERA was created.
"What's the odds of shareholders winning that battle?"
Again, depends on whats being sued on.