I suspect that BI doesn't take "phalanx" either...
Not necessarily I noticed the BI unit file has all the formations from RTW in it (new + old) while the 1.3 RTW file still only has the smaller RTW set. In BI there is not a problem adding the phalanx to a spear unit (admittedly I just tried it once, so I don’t know if there are issues when the unit fights etc.). More promisingly on the issue of modding BI back in time, I’m pretty sure SigniferOne felt his over-arm hoplite model was compatible with BI shield wall formation, but I haven’t tried it yet.