For arabia could be some form of comp bowman. i have no clue about egypt and for turks, some form of the cavalry they used at manzikert.
Remember that Manzikert was less of a battle and more of a debacle. The Byzies disbanded the Armenian army of 50,000 just before the battle and the Byzantines, disloyal to Emperor Romanus IV, retreated, and Romanus was captured since he really had noone to help him. I still think the Qapikulu would be best.
(Offtopic)
Drtad, it sounds like you know about total war modding, i got Medieval II:Total war recently. is there any way to play as byzantium? that was one of the reasons i got the game.
What you do is you either win a campaign as Venice (or something like that, you can unlock all the factions like that), or you can open your descr_strat text file (you can do a search for it to find it, I can't recall which folder it is in, probably world/imperial campaign or something of the sort) and you cut Byzatium out of the "unlockable" section and put it in the "playable" section. You can do this for any faction (besides papacy and aztecs) that isn't playable from the start. Or you could download a mod, all mods automatically allow you to play all factions and plus add more goodies. In your case I'd suggest:
Copy this link to go to the mod "Deus lo Vult" which adds Armenians, Flanders, and some other stuff.
http://www.twcenter.net/forums/forumdisplay.php?f=309
Or Stainless Steel mod which adds the Templars, Kievans (also has Novgorod), and Aragon.
http://www.twcenter.net/forums/forumdisplay.php?f=314
Or the SicilianVespers mod which has a Late Era campaign and adds Bulgaria, Armenia, Serbia, Aragon, and the Angevins (Anjou in Early, Naples in Late). Btw, I am a part of the Sicilian Vespers team, and the next version to be released in September is much better than the current release, so you could wait for that.
http://www.twcenter.net/forums/forumdisplay.php?f=354
I hope this helps, Ajidica.