Nope, not in another trial. If he can be called as a witness for any reason in this trial he cannot be an advocate.
And the judge has taken the prudent step of ordering an investigation.
Sounds like she’s doing it right.
You'd just keep doing that until the defendant had no one but drooling idiots to defend him.
What you can't have is a lawyer electing to serve as both a witness and counsel.
The judge is in over her head and wants out of this one ~ she just stepped in it.
All that happens is the trials (of the 37) get delayed and if they're old enough some of them will die, etc.