Before or after we have pizza?
Using eggplant instead of a regular crust would make it more like moussaka than pizza. But you’d still need some white sauce. (I do love moussaka too! :o )
BTW, I’ve had seafood pizza with béchamel instead of tomato sauce. It was superb!
Wow. You consider eating 900 calories of pizza over the course of your entire day, “going batshit”? 
So far as I have been able to determine by search and by experimentation, there is no such thing as a healthy pizza for me. I am on a very low salt diet. Every ingredient of a pizza is salty, and subbing all or most of them makes it basically ‘not pizza’.
Vegan cheese substitute isn’t that bad…it’s not quite the same texture as cheese, but it’s definitely not tofu-like. It’s very tasty with a good tomato sauce and lots of veggies.
I’ve also had cheeseless pizzas that are very good. Surprisingly, the toppings pretty much stay in place. One of these cheeseless pizzas used hummus as a substitute for tomato sauce – very good with veggies, as long as it isn’t cooked too long.