So on mags -- I just want to reiterate how GOOD VZ58 mags actually are.
Basically, they have the weight of AK bakelite mags as well as the strength of AK steel mags under most field use conditions (i.e., where you're not testing to failure limits).
Unlike steel, the VZ58 aluminum mags also have much less issues on the front of corrosion.
And one feature you'll see on the VZ58 OE mags is that they have a shelf at the top that interfaces with the receiver (preventing over-insertion including when under abuse) that OE AK mags and most aftermarket lack.
Main thing to keep in mind is that the Soviets wanted the entire combloc to standardize on the AK -- the VZ58 would have only have been granted an exception if it met OR EXCEEDED the AK47 across all testing parameters.
Also on FAB, I'm pretty sure they both weigh more (slightly) and cost more than surplus, as well as being less durable. I think there's a place for them in low mag capacity states -- as mentioned in CP's post, I think the base plate allows for the use of FAB's AR mag coupler (believe it's for 3 mags), but they only make the 30 round mag version AFAIK.
Offering in 10 and 20 rounds at same price point as current would be awesome. And I most definitely think it would open up a market niche and demand that's not there for their current weapon -- reduced rounds = less weight, which means the polymer configuration should be less prone to shearing under most circumstances as well...