SO, a historically accurate phalanx would be an axeman replacement with:
Strength 5, +75% vs melee, +100% attacking mounted, -25% vs archery.
Okay, based on this:
Phalanx
Strength: 5
Movement: 1
+75% bonus against Melee Units
+100% bonus against Mounted Units
-25% bonus against Archery Units
Replaces Axeman
Thus, when attacking Melee Units, it would receive 8.75 STR; When attacking Mounted Units, it would receive 10 STR; When attacking Archery Units, it would receive 3.75 STR.
When defending a city with no promotions, an Archer receives 4.5 STR. This gives it an inherent .75 STR advantage. Not much, and if you give a City Raider I promotion to this Phalanx, it receives only a -5% (-25% from unit +20% from promotion) discount, creating a Phalanx with 4.75 STR versus an unpromoted Archer defending a city with 4.5 STR.
Plus, when using Alexander (who's still Aggressive in BTS, right? Haven't used Greece much in BTS), it'll receive Combat I automatically, opening up the Cover and Shock promotions, as well as City Raider.
Thus, using Lord Olleus's historical model, we have an Aggressive Phalanx which can get Cover, negating the Archer deficit.
Not to be annoying, but that seems a tad overpowered.
Based on the analysis, I would propose a still slightly accurate Phalanx model:
Phalanx (Gooblah's Version)
Strength: 5
Movement: 1
+50% bonus when attacking Melee Units
+100% bonus when attacking Melee Units
-50% when defending or attacking Archery Units.
The last line forces the Phalanx down to 2.5 STR when an Archery Unit comes around, giving the Archer an advantage both in terms of Rushing
and pure defense.