Their essay on composite infantry types is interesting as a Crusader Kings II player, because the game has tons of historically accurate mixed units you can recruit that combine archers and heavy infantry/pikes, but virtually all of those units suck because the combat mechanics still enforce a rock-paper-scissors dynamic.
Specifically, every 15 days, your army rolls a "combat tactic" (based on number of troops) that buffs certain types of units and nerfs others. "Advance" buffs heavy infantry, "force back" buffs pikemen, and "charge" buffs cavalry. Then if an army uses "advance" goes up against "force back", they get an additional boost. Likewise, for "force back" against "charge" or "charge" against "advance". There are also archer-specific tactics that don't play a role in this triad.
The simplified combat tactics to enable rock paper scissors matching is what makes the historically accurate archers + pikemen trash. No matter what combat tactic I roll, I would rather have either additional archers or additional pikemen because only one gets boosted at any given time. The game does not model the mutually reinforcing nature of diverse armies because it could break the rock-paper-scissors triad that says certain troops should defeat other kinds of troops.
In fact, having a diverse army is penalized because you will "roll bad tactics". If I used China's 250 archer : 100 pikemen retinue, they will correctly alternate between pike (the force back tactic) and shot (barrage tactic), then get slaughtered by another army that had 250 pikemen : 50 archers because their 250 pikemen was getting buffed 24/7 by force back instead of having to share the limelight with my archers.
