Formations can't be that hard to code. "Column" "Line" "Wedge" "Square" that's about it.
And yes, they are INCREDIBLY useful even in this small of a game. Imagine a phalanx formation of ~12 pikemen, quite useful. Supported by a few cavalry and the rest infantry.
This, of course, works better with battle-size modded to 60 or 80 or 100.