This the cuestion.
Why we want to make this system?

Only because we can, or for learning some useful?

Emulating exactly an old computer. No if we want this then go to ebay and buy the real system, not?

Make a very good 8 bit machine using obsolete and discontinued cards? Then all we learn doing this proyect is only for enjoy and we can't reproduce the experience again.

If we make the system with standard and market aviable chips then may be some parts of the work will be usable for new real proyects.

For example, if we can do a graphic chipset on a single '52 with a useful characterist then we can reuse this if we need a display but we can't asume the cost of an equivalent LCD.