Crust exists solely as a delivery method for toppings

Oh, no no no, crust is very much part of the deal. This is why pizza only really works when done in pizza ovens. A really well baked crust, not too hard, not too soft, the right level of crispyness, really makes the pizza and brings out the toppings.

Definitely with your top tier, except maybe broccoli. I like broccoli, but on pizza.. bit meh. But for a good vege pizza, mushrooms are the sine qua non IMO, unless you go for a pure Margharita.

What are your thoughts on Gorgonzola?