No just change the scale factor.

JRock, forgot to answer before.
You can't mod the the layout of the soldiers in the unit, and still play online with unmoded people. Changing your stats so you could fit more people in a smaller space would give you a big advantage.

You can however customise the historical battle formations, and the group formations. The layouts for these are all kept in plain text files in the formationData folder.
I'm not going to explain exactly how to edit these, as describing the whole system would take a lot of time. I'm sure some of you brght folks will work it out though. Any custom layouts you make should ( by which I mean it's never been tested ) work online.