It could be done, and I think it would be cool, but I think it would tank.
The market for "Alt-5.56"s is not very strong, and FN would be more likely to be slitting their own throats by siphoning off potential SCAR sales than really being a serious contender.
How much would they sell them for? Or perhaps more importantly, what would they have to be priced to be competitive with ARs?
How many "Alt-5.56"s have been attempted and released to thunderous fanfare, only to trickle out the doors, and die an ignominious death, often right before quietly being taken off the market?
::shrug::
I've fired plenty of FNCs and AK5s and have always found myself wanting my M4 back, and being super unimpressed.
I think options on the market are good, and I think it'd be cool if the FNC was more available, but I certainly wouldn't buy one, and I suspect their "popularity" has more to do with their rarity than anything else, in which case, if they were re-released, much of their cachet would disappear, and they would languish.
~Augee