I don't really know much about this but I want to see Linus/Anthony hook up a Quadro to a Pi.
Here's the article.
From people who don't really want to read the whole thing here's a brief overview: Replace the USB controller with custom pcb to allow for PCIe over USB or maybe a wild Anthony will make a custom pcb, then hook up a usb cable to a weird pcb with two PCIe 16x slots.
My first post by the way!