I have a solution to the genuine problem of long fraud trials and the alleged problem (very upsetting to prosecutors) of frequent acquittals.
The prosecutor should have a maximum of three hours to explain the crime. Not produce evidence, just explain what is alleged to have happened. If, at the end of that time, the jury does not understand the crime, the case should be dismissed. It is self-evident that there is reasonable doubt as to mens rea on the part of the defendant.
Does this mean some people guilty of complicated frauds will go free? Yes. But the law applies to everyone, not just the professionally qualified. If a jury cannot understand the law then the law needs to be amended or repealed.