Just for the hell of it, I wonder if anybody has ever considered the sidecar->zorro II mod and then shoved a Blizzard 2060 fitted with a 150MHz 603 PPC prototype board in there?
That would be one hardcore A500, though I suspect a tower case may be called for 
not a 2060 in there yet, but someone did a
sidecar->zorro2 mod ... only a GFORCE'040 there it seems.