I couldn't agree more with your proposition. Bloomberg has sociological and psychological advantages no other candidate has. He can attack Trump from the very space Trump believes belongs to him (and fantasizes that he owns). An attack coming from this intimate terrain is much more traumatic for Trump. He won't take it well. (I've been speculating that Trump wouldn't even debate Bloomberg.)
Also, Bloomberg can bypass Trump's defense mechanisms to attack him at the very pit of his being.
Bloomberg has no fear of Trump--not in any way, shape or form. There's actually nothing Trump can do to Bloomberg.
Not to get too psychoanalytic, but an attack by Bloomberg on Trump could reawaken Trump's terror of his own father. So I think Bloomberg can hit Trump at his weakest point, a point he tries to protect and that no other person has yet successfully hit.
Here's a post I made some time ago. It's a little old, and I would change some things in it, but it's substantially how I see things:
https://www.democraticunderground.com/1287420520
But I love this topic! We don't talk enough about locating Trump's weak points or how to exploit them. Thanks for your post!