Ok, maybe what I'm trying to do is not possible.
Everything is possible if you have enough money.

In other words, can a file containing characters in the ASCII range 1-255 that is created on a Mac, be opened in Windows, then translated automatically(by my program) into iso 8859-1, and then displayed the same as on the Mac?
Surely yes if you are talking about plain text files. If you can write a program for text conversion you can create your fonts as you wish, with any encoding.