Legend of the Five Rings did this a decade and a half ago.
So did D&D. So did a lot of games.
No, D&D never did it the way L5R did. It was considered pretty innovative for its time. I think a lot of game designers could learn from it and that's why I mention it. It's mass combat where the rules governing PC actions are 99% the same. I'm not exaggerating with that number, even in the case of adapting it to Pathfinder. The only real difference is some environmental damage based on armor and bodyguards, and the list of ideas for heroic opportunities (which GMs and potentially even players are free to add to) - which are all straight up encounter scenarios, to a one.
Pathfinder is a more complex game than most of those though, and it doesn't really help me if a system exists for a different rules set.
I'd bet that before you came up with troops you'd say the same thing about 7th Sea's squad system.
No, it won't port over perfectly - troops are not an exact copy of squads, and you wouldn't want to default to each player deciding how engaged they are individually in a Pathfinder equivalent to L5R's battle system. Combat resolution is fast and deadly in L5R. So, instead, just default to leaving the group together, and adjust heroic opportunities/duels accordingly.
The ultimate idea, though, is that a GM who lays things out is going to have a good understanding of which side entered with the better strategy, which side is having more of an impact, etc. so it comes down to heroics on the part of the PCs to change what will logically occur - for better or for worse.
If not, you can have some loose guidelines to resort to die-rolling to decide how strategically advantaged a position is, and then dive into heroics from there.
As for your complaint about adding another skill... *ahem* Profession: Soldier. At least it's not as silly as Craft: War in 1e Exalted... I don't think adding Tactics is too much of a burden. You could roll Appraise into Profession: Merchant and see who bellyaches.