I woldn't go so far as to say it was "prophetic". Contemporary DEC PDP-8 (OMNIBUS) and PDP-11 (UNIBUS / QBUS) systems have a similar approach to "interoperability", where cards for peripherals were also mapped into the machine's address space. It was great that Woz saw the utility of this and brought it into the homebrew/microcomputer design.

I understand that Steve knew about that but trying to create an inexpensive computer, working with hard trade-offs makes his decision very wise and smart. We can know about complex architectures but it might be very difficult to copy them in cheaper devices.

I think it was more driven by his own desire to not limit what future hardware hacking he wanted to do with this computer he just designed.