I like your proposed army composition, looks to be pretty varied but effective. If you end up having your "discretionary unit" in any of your armies be infantry, may I suggest using Thraikioi Romphaiaroi (sp?), you will be able to recruit them in Tylis and Naissos from the level 4 regional complex. They make good flankers that can also act on their own if necessary, and they just shred through armored infantry. From your last post it looks like you know how to deal with Seleukid phalangitai (about the same as you would Makedonike phalangitai), but you are going to need someone to deal with the Agema Thorakitai that the AS will be bringing from Antiocheia, Romphaiaroi will shred through those armored foot tanks (they are spear armed so Prodromoi aren't gonna cut it for that one). It's also likely that you'll have to face off against the Ptolemaioi once or twice, and the Romphaiaroi will deal with those Galatian armored swordsmen the Ptollies get pretty nicely.

Good Luck on your new campaign.