I think the existing expansion ports on the PIV do actually use the PCI standard, they're just in an unusual form factor. As you can see, there's not a whole lot of logic on the prototype full PCI expansion busboard. Probably wouldn't be too tough to create again.
On a different note, that Picasso Classic looks really cool! Shame that never came out. Imagine if there was an easy RTG option for A500s. That would have been a huge boon in the mid 90s.
