You are correct on many counts that you stated. As far as accounting standards, there is quite a breath of variations that are allowed for property assessment. But from what I have researched it is quite a stretch to increase a property value by more then 25%. And it has been rumored that the Trump organization has valued some properties at 2-3 times their assessed value. On multiple occasions Trump has stated that there is value added to some properties because of his name. And NY State does allow a increase for “name branding”. However from what I have read there must be the proper tax documents filed to do such a thing and the Trump Organization failed to file that paperwork.
I agree that it will be difficult to charge Trump directly. From what I have read he does not use email, or send note or email. Everything is done verbally. So I agree that it will be difficult to prove that he directed any illegal activity. However if the DA;s office gets a high level official to flip it might be a game changer.
It seems that the tactic is to go after Allen Weisselberg since he is the CFO. And if there are discrepancies that can be proven out of bounds it could lead to fines and penalties on the Trump Organization.