Seems to me the normal development of a variant from an existing design would follow the path of simple to complex.
7.62X38 Variant
Step 1 - Build new upper only.
Step 2 - Test the crap out of it with XCR magazines - Sell the resulting product (New guns and conversion uppers) to fund Step 3.
Step 3 - Once sufficient manufacturing numbers have been achieved selling original .223 version and new 7.62 version proceed to step 4.
Step 4 - Build the "world version" using AK magazines by redesigning lower.
I believe the point of the whole exercise is to determine if there is sufficient interest in Step 4. However, I have been known to be wrong in the past.
Step 3 would be a given during the normal development process.
Not to sure I understand the STANAG issue people are chiming in with. Might be a problem with 30-40 round magazines and the required curvature to maintain correct alignment with 7.62X39.
However, at 10 rounds , the XCR magazines are the same length as the "Straight" portion of the curved magazines. Have never had an issue using them (all 10 rounds) with my B&T conversion of my CZ 858.
Work like a charm.
L