Now that I think about it, the only time we will see armies are in year 2. I am not sure what to think about this. Maybe not an army but unspeakable horrors? Not sure, Makuta is portrayed, mainly, as a manipulator. So could easily have someone else’s army fight for him. It is important to note though, latest cannon suggest that the cast are fond of the idea of having the corruption of the elemental powers be the reason for the Rakshi mutations.
Either way, I personally want a Makuta army to play with. However, I am not sure if the story will allow for such a thing to exist. The next best thing is having a bunch of people with corrupted elemental powers form a sort of army to fight. Either way, we already have and army rallied by the regions fighting a civil war. It would make an interesting plot twist if suddenly a portion of each army turns against them and they have to unite to survive.