What would be more interesting is if attack strength didn't scale 1 to 1 with squad size. Essentially, not everyone can get into the front rank to fight in larger units, so there should be a scalar on attack strength at least.
Essentailly 1-3 in unit = 100% attack strength (attack *1-3).
4 or more in unit = +.5 to attack multiple per additional member, i.e. 5 members in unit adds 3 + .5 +.5 = 4x to attack.
Or some fancy scalar (Example: 4th member +.5, 5th member +.4, 6th member + .3 7th member +.2, 8th member +.1, additional members over 8 adding no additional bonus to attack)
A simpler 'scalar' might be + .5 per member over 3 (to 6), +.25 per member over 6. So a 9 member unit would deliver x5.25 attack (3 + 1.5 + .75), and a 12 member unit would deliver x6 damage [3 + 1.5 (3x.5) + 1.5 (6x.25)], using this progression.
Larger units will (as usual) take more damage to kill (more guys to kill), but will also no longer deliver overly massive attacks in one shot, using this mechanic. Larger units will last a bit longer in this environment, than they did before when facing each other, but I don't see that as a bad thing...
This would make a 9 man unit under the +.5/unit rule over 3 equivalent to a 6 man unit r.e. attack strength, with more guys available for damage purposes.
This becomes important because, as more members are added to units, Sovereigns and Champions get further outclassed. They simply can't compete as effectively in a damage x9 environment, if say 9 member units are allowed..
This could also be varied by weapon type (i.e. spears lend themselves better to 2nd rank attacks than swords do), but that would be hard to accomplish with just an hour or so of coding... this would be a goal for one of the next DLCs I think...