As the title suggests, could there be other non mercenary NA2 armies like the JSA? It could be used for smaller powers, such as other nations on Earth, that lack the size to have multiple sectorials.
I think that there's definitely the possibility, but I doubt any are currently planned. NA2 is just kind of the catch all category for things which don't fit under others.
I like the idea a lot but don't think it's doable for the moment. There's already so much! A little off topic: Personally I feel NA2 forces in some way, should be able to declare themselves for certain factions in campaigns other than NA2. Meaning for instance. A Dashat company declares it's working for Yu Jing in a campaign. Or White Company for Aleph, etc. Some like JSA, would only be able to for themselves.
We did that in a couple of custom narrative campaigns, actually, and in there NA2 could choose who they work for.
I would love to see an independant merc company that doesn't go into the usual Private Military Corp scheme, kinda like Druze a bit but even more developped into the shady business field, with skirmishers, hacking and other camo game. To me that's one of the problem of armies like the JSA (or even Spiral Corps to some extend): they shouldn't be NA2 at all but their own faction, since they can't fit the merc/non-aligned narrative at all (plus they are even as well developped as Tohaa or O-12, the later having their own full faction with -useless- sectorials). That's also very limitating them in further lore development unless you give them their independance, which then makes the NA2 label very unfitting and inappropriate.