The Records (http://wiki.battlemaster.org/wiki/Records_of_BattleMaster#Characters) show that the largest unit ever was 320 men. I would say the smallest width possible could be around 600 men. Then there would always be room for more than one unit, and even with smaller units this corresponds to 12 units of 50 men each, hardly a blob.
I think the goal here would be to replicate Agincourt, not Thermopylae.
I'd love to replicate both, and I would suggest that there are a number of realms where 600 men might be their whole army, especially on a long-distance campaign. Hell, I remember that when Arcaea was fighting Zonasa on FEI, we only got 1000 men into our army once, every other time was fewer. Now, granted, we were using mostly high-end troops, but still.
