Why are you making this so hard on yourself? If you want to add more memory internally why not just buy one of these? 4MB + IDE support for $64 USD. Or 8MB for the princely sum of $74 USD. Since it connects directly to the processor this will be real fast ram (like through the side expansion slot), not that fake "slow-fast" ram. But it's your Miggy, do what you want.
I think he just wants it as authentic as possible for it's time. Like me a bit, I still like my real hdd's. If he wants a modern true fast ram, then the kipper unit is ideal, so the choice is there if he wants it. This would make a 2mb chip plus 8mb fast m/c... Nice A500.