It is realistic. I worked on a cross-platform product for nearly a decade that followed a methodology very similar to this. Our code worked on 16-bit, 32-bit,

It is realistic. I worked on a cross-platform product for nearly a decade that followed a methodology very similar to this. Our code worked on 16-bit, 32-bit, 64-bit, big-endian and little-endian systems. Following these rules did not slow down development noticeably. In fact it became second nature.