Bad idea.
This will play havoc with the battle code. So your line is max 600? Then for 90% of the battles it won't matter at all. For the really large ones, however, this will happen:
500 men of one side move into the square, distributed over several units. Now only 100 of the enemy can move in and will, of course, get slaughtered. Next 100 move in, get slaughtered... players complain.
At the absolute very least, the maximum has to count seperately per side. Everything else is a bad idea.
