I'm aware of several different constraints on the Pi5 (and beyond), and I was hoping someone could give the full list and what specifically prevents such a feature (and why).
The next Rpi will still want to keep the same footprint as the previous ones, and the designers also won't want to remove features to include a coprocessor socket (they would remove features possibly to include more sophisticated substitutes... USB4 instead of USB2 maybe).
They want to keep the cost down (though how far down is unclear).
And any new features would have to have some use case for their primary goal, I think (low cost educational computers).
On top of that, there would be wattage concerns as well, if any potential use required that it was more than 15 watts (less?), that'd scuttle the idea too.
Finally, they'll certainly want to use some ARM core or another (for that matter, even a Broadcom fabbed one, I should think).
How do these (and the other constraints I might have missed) make such a feature unviable? Consider that a coprocessor probably needs at minimum 250-300 pins for any reasonable use, and I can't find anything anywhere that uses less than a square inch of space for that. The cost for the socket alone will be significant (but I can't even guess what at their volume). There are only a few candidates for a coprocessor anyway (perhaps an FPGA, or a some older x86 core die-shrunk down really low).
I know this is a dumb idea, but I'd like to know in detail all the reasons that it is dumb.