Yea, I could see text clutter when zoomed out. But on max zoom, I think it should fit nearly every time. It's rare that you have 20 armies in the same region. Though granted, it does happen now and then, when big alliances clash.
Perhaps it could be split into two options one can check. Like realms and duchies, which are two overlapping layers if different hierarchies... Well one option could only show totals by realm, and the other, more precise, by army. Possibly with a frame that depicts your realm's diplomatic relations with that realm.
Regarding access to information, ease of access is a double-edged sword. Right now, any noble in a realm can click through region details, and compile a list of all of the militia and mobile forces in every single region that realm possesses. But the time this would take, and how utterly tedious it would be, dissuades people from doing it. If any random schmuck could join a realm and get access to detailed compilations in an easy-to-share screen capture format... then the likeliness of people doing it for spying dramatically increases. As it is, I think everyone has access to the "troops" layer? But it's not very intuitive or informative, which means spies don't bother to share it (if they even know it exists, I just discovered it today). On the other hand, since it's not very intuitive or information, it also makes it completely useless, and thus nobody at all uses it.
I'd rather it be informative and useful, with checks to prevent abuse.
Also, the way I see such things, is that it applies to everyone equally, thus self-balances. It's just a utility for every side of any given war to use, and helps realms that have a hard time recruiting able and active people by making the job slightly less demanding, while just easing the burden on those players who do take the time and effort to be active marshals and generals.
