I have seen some screenies of guides and AARs (notably Quintus Sertorius ones) in which the roman army is deployed in battle in "quinqunx" or chessboard fashion. To the best of my knowledge, this way of arranging the line for battle is totally wrong: historically, the posterior half of any manipulus would close the gap before engaging so that the roman infantry presented a single line to the enemy. It is illogical to think that one could present a battleline full of holes and not expecting the enemy to enter the holes and flank each and every single manipulus. The enemy was not thinking "Oh, a gap through their line. But wait, it's the quinqunx. Let's keep the frontal slaughter". Too simplistic. Instead, the same process was used to bring new and fresh soldiers to the front while wearing down the enemy.

A very precise idea of this can be seen here. The footage is about post-marian legions but you get the idea.

In gameplay terms, the best one could do to represent the chessboard tactic (what I sometimes do if I feel particularly inclined) is to first deploy the standard triplex acies (with a single battleline for both hastati and principes), then to thick each unit with the ' and ì buttons (at least that is my keyboard configuration), then again to re-thin them to the original number of ranks to close the gaps before engaging the enemy.

Any thoughts?