cool project man, but why not just buy a used 501? not like they are rare lol
This could actually be quite interesting for internal expansion. You could implement something like the kcs PowerPC, or ide or whatever.
The interesting thing about the KCS PowerPC is they made an A2000 adapter card
http://www.bigbookofamigahardware.com/bboah/product.aspx?id=336 which converts from zorro 2 into the RAS/CAS memory accessing of the a501.