How to play the Seleukids as realistic as possible?

[Titus Marcellus Scato]

Have a look at the TWC House Rules thread for EB:

http://www.twcenter.net/forums/showthread.php?t=468934

Here's the quote for Arche Seleukia - note the one about moving the faction's capital to whatever city the faction leader is in or nearest to:

1) All types of factional phalanx units should be used.Pantodapoi/Machimoi Phalangitai should be used in every army, even a mobile professional one. Klerouchoi Phalangitai should also be used in most armies, though in slightly lesser numbers than aforementioned levy phalangites (but the ratio can switch to favour the Klerouchoi as the campaign progresses, as more settlers are available). Pezhetairoi should be severely limited for these Eastern Diadochi, and used only in small numbers in mobile armies; the same goes for Elite phalangites. However, when you feel your Empire is large enough, you are allowed to field a single "Royal Elite Grand Army", that has 4 units of Pezhetairoi and 2 units of Elite phalangites in it's ranks
2) Thureophoroi and Thorakitai should be limited in the early game.Peltastai should be your primary javelin/melee troops supporting your Phalanxes. Maybe a single unit of Thureophoroi could be allowed for mobile professional armies, but not for garrisons. I'd even say that Thorakitai should not be used in the early game at all, as they were a late innovation afterall. But as time passes by, you are allowed to gradually increase the number of Thureophoroi, and also add some Thorakitai to your armies
3) Archers and slingers should not be used in any real numbers. As this eastern Diadochi has to face many missile troops, more of those are allowed in their own ranks as well. However, these should primarily be foreigners (Persians etc.) and mercenaries, while the Greek "Psiloi" units mentioned earlier should be limited for this faction as well.
4) Armies should be composed primarily of factional troops.this faction naturally has more leeway in this, as their access to native Greek units is more limited. But still, maybe a maximum of 8 foreign units should be applied to armies operating in your heartlands, and even in remote areas there should always be a few factional units present in every army (so that the foreign mercenaries would always remember who they're fighting for).

My rules for Seleukids, I just sort of went along a mental note never put them in print before, so I might add to them later if I play a campaign.
A Strategos for each Satrapy
Keep the core of the dynasty Makedonian
Allow local Satraps in the eastern Satrapys
A satrap can only campaign against local threats
The Basileus must lead the Royal army on campaign against large foreign threats
Therefore only one full stack of 'Royal army' only
No destroying of enemies, or expanding ahistorically
No reloading battles if defeated
No time travel on campaign map- don't go back to an earlier save- unless CTD
The capitol moves to where the Basilieus is- this helps to simulate revolts that occured when family members or Startegos of satrap knew Basileus was away on campaign
If a Strategos (Satrap) loses his army- cannot take troops from neibouring Satrap, must wait for the Basileus or a high ranking family member