So look what I did:
Not as good as it looks though. All I did was disable ports 2-4, then put them all in x4 mode.
So my port 1 is the expresscard slot, 2 and 3 are mini pci-e slots. My wifi card is in port 3 and port 4 is the network "card" (it's integrated into the MB so it's not really a card). I tried just setting the PC to x4 with the wifi and network card active and it results in an instant crash. My network card dropping out when overclocking gave me the idea of disabling the wifi and network card, then with nothing active on ports 1-4 try activating x4 mode. It worked. This is great because it means that I could wire an external card to port 4, and just turn off the network card and activate x4 mode when I want to use the external card, and the opposite when I want to plug in an ethernet cable. I found the datasheet for the network chip and got the pin numbers for the pci-e. Now all i have to do is find the chip and connect wires. Hopefully it isn't too small to hook things up to. I have a usb wireless unit so I'll still have internet with the wifi removed and ethernet turned off.
BTW I can overclock the PCI-E bus by 22% so I'll have basically x5 pci-e bandwidth if this miraculously works.
K so I need some way to get the mini pci-e signals to the card. The mini pci-e to zif converter looks nice but I'm not sure how I would know which signal was which in the ribbon cable. The hwtools mini pci-e stuff seems kinda expensive.
This looks doable! Just a lot of work.