Third, the design has to be very generic

Ah, the famous "generic" board

I have yet to see one such, that did not fall at the wayside on the 2nd or 3rd app.

There have been cases of "smokescreens" from those that insisted on being stuck in the past and still wanted "advice" but OK, on the assumption that you are genuinely and truly part limited and not just stuck in the past because of buying an old (3 years is old in tbis industry) book let me comment on what you are doing.

-> 1 X 8K SRAM (@ 0000h ~ 1FFFh)
-> 1 X 32K SRAM (@ 2000h ~ 9FFFh)
the decoding is so much easier if you make it
-> 1 X 8K SRAM (@ 8000h ~ 9FFFh)
-> 1 X 32K SRAM (@ 0000h ~ 7FFFh)

why
-> 1 X 32K FLASH ROM (@ 0000h ~ 7FFFh)
the 89.. chips have internal code flash

-> 8259A (PIC Interrupt controller)
-> 2 X 8255A (PPI)
-> 1 X 8279 (Keyboard & Display controller)
-> Auxilary Output port (74HC573)
-> Auxilary Input port (74HC245)
what do you need the interrupt controller for?
instead of the 8255 use several Auxilary ports as you call them
the kbd and display is so much easier (canned code available) if you use straight MMIO through an "auxilary port"

Erik