I think the main cost compromise would be being able to use standard AK mags rather than training. Again Type 81 already had Bolt hold open standard and China was pretty poor back then. Also note that Type 81’s hold open does not have any external release unlike AR15. There’s no reason to believe that they would get rid of a feature they already implemented in a far older design.
That's a good point, magazine compatibility may indeed be a more pressing priority.