Anything's possible.
I imagine the lower would end up a lot like the AK, with stamped sheet metal sides riveted to machined trunnions to hold the stock (buffer tube) and in the front maybe the pivot pin, or maybe the whole magwell. would depend on how "stamped" you wanted it.
The upper would be pretty easy, just make a stamping and fold it kinda like a G3 reciever, and then rivet or weld it to the barrel extension. It would make barrel changes less fun. (kinda like other stamped guns actually). I'd probably wld a tube in the rear for the takedown pin to go through. (Again like the G3).
It wouldn't really serve a purpose other than the "look I did this!" but it's doable.
ETA: As far as non original AR recievers, I REALLY like the "bolt together" one that has pictures running around. You could make that with a good drill press and saw.