I hope it's not too presumptuous of me to post in this thread so soon after becoming a citizen, but I do enjoy everything to do with court systems.
Firstly, in my mind, it is undoubtedly incorrect to use "amicus curiae" as shorthand for "amicus curiae brief". "Amicus curiae" and "amici curiae" refer exclusively to the person or persons making the brief. If we mean the brief, we should say the brief.
Secondly, I think it is inappropriate for the court to consider amicus briefs in criminal cases. In such cases, they don't serve any purpose beyond being character references, which could just as easily be obtained by the prosecutor and the defendant calling interested parties as witnesses. If the court is hearing a constitutional or public law case, then I believe amicus briefs could certainly help the court determine the legal matters in dispute.
Lastly, I am very uncertain about section 5. It says "As such during the trial any party that has a lawyer may be called as witness." I am not sure about what rights the defendant has in Wintreath, but this would seem to go against the principle that a defendant is entitled not to incriminate himself. If by having a lawyer he is compelled to testify, then that would seem to abrogate that principle.
In the same section, I think the provision that the trial is "dismissed" as soon as a defence lawyer stops being the defence lawyer is a recipe for disaster. I think it is far better to say that the trial will be automatically paused for 24 or 48 hours (without a vote of the judges) in order for the defence to sort out a new lawyer. If the defence gets a new lawyer before the expiry of that time period, then the court should be authorised to start earlier. If the defence doesn't find a lawyer in that period, then the defendant should represent himself until he can find one.
That's my two cents. Or maybe four...