Like said on the first page:
ACA500 does not allow any other expansion than a chipmem expansion. As mentioned yesterday night, the lower 68000-adapter will block the 86-pin port to send a clear message: Nothing allowed here. Further, the 68000 socket will have to be empty, otherwise the mechanical mounting concept won't work.
During the Amiga life, noboby take care about the fact that is was not possible to plug A570 with A590 with Supra 28... You have to make choices. Here, the choice is to add A1200 expansions.
In all cases, the A570 is like the CDTV drive. Today, no more work properly or will fail in few years.
It's more a collector item and the price to get it allow to buy a second A500.
Finaly, the ACA500 IDE controller will allow to connect a far cheaper, better and faster CD-ROM drive for peoples who always need that today...