How to play the Seleukids as realistic as possible?

[Titus Marcellus Scato]

I don't know if it's realistic but when I'm dealing with steppe armies I simply don't bother to include any phalangites at all. They can absorb arrows very well, but that's about it - the infantry units that steppe factions use are generally mediocre or less, so thureophoroi are preferable because they're more mobile and versatile.

Levy phalanxes can be useful against the enemy bodyguard cataphracts, because of their armour-piercing axes. But I put them in the rear, with missile troops in front, so when the enemy charges my missile troops withdraw and the enemy cataphracts plough into the phalanx and get bogged down in melee, I then turn phalanx mode off and guard mode off, and the men down their pikes and get stuck in with their axes.

But against light horse archers, phalangites are utterly useless. Especially mine since I've modded their shield value from 5 down to 3 (small shields).