I happened to have a thought, and I'm sure someone has thought of the same thing in the past; a couple of cascaded 8 bit magnitude comparators that would activate the /WAIT line when the address is detected. It could be hardware controlled via switches, or software controlled via 8 bit output devices. I figure you could even setup the comparators to act as a type of memory protection if the address is between two values. Just a thought that I might pursue at some point. I'd be interested if anyone knows if this has been done before, and who did it.