If we can only replace just one affix per item, why can’t we replace a greater affix with another greater affix? IMO, this should be a thing; dropping an item with 2-3 GA that is appropriate to your build is very difficult. Replacing one GA with another one would make things very interesting.
This could be a new affix on an item. I made it a long time ago. ITs a light blue text color and called an enchanted affix. This affix keeps its GA on enchanting and is cheaper to enchant roll.