lol, I'll definitely give you credit for ambition and enthusiasm, gamefreak. I was just thinking... I'm not sure what Bacteria did to make his multi-system interchangeable, but I was thinking ISA or something similar might be an interesting route to take.
Let's take ISA for example. It was an old I/O standard on PC motherboards back in the day (the predecessor of PCI/e/2). If you look at it, you have 98 joints attached directly to it through the back of the motherboard.
I'm just spit-balling, and I am fairly n00bish with the soldering, especially on the modding scene, but it seems reasonable to me that we should be able to cut the ISA slot off of the motherboard and solder it up to all the common components of your multi-system. You would have to figure up about everything in advance, it might be a pain in the ass too... For example, pins x-x for controls, x-x for video, etc, you might have to isolate sets of pins for system-specific stuff... Then solder the system-specific components to the corresponding pin on the male contact.
Here's some quick pictures:
This is the ISA slot from the top of the PC mobo:
The same ports from the back:
And finally, the male contacts:
The same concept would apply to other standards (pci, etc..), except that when you look at the male contacts of a pci card, you'll notice that it'd be a complete pain in the ass to work with unless you're particularly good at soldering to tracers...
Also, you guys might keep in mind that I run a computer store here in KS, so if you live in the US, I should be able to get you some good deals on this stuff if you want to experiment with it.