^^^ Lots of good points and thoughts

. Some comments:
Offmap resources for Lebannon etc? I did not realize that! <does some research> it's in db\events\ai_revolters.txt, for people who are curious. (I've altered my copy of this mod to include an Arab Caliphate, and I was wondering why Damascus and Beirut had no economy, so this is quite interesting.)
You make an excellent case that industrial values in the east should be higher, but on the other hand it's arguable that industrial values in the west (Athens, Thessaloniki, Tirana) "should" be lower. Athens was as big as it was because of, for example, the refugees from Smyrna etc. in the 20's: it probably wouldn't have been as big in this timeline, much less bigger. On the other hand, it might have had a bigger economy...
At the end of the day, how big the Empire's economy should be depends on gameplay, since this is a really,
really hypothetical scenario. I've experimented with playing the mod with lower levels of IC, and it's much less fun. I did find that including Bulgaria in the Empire from the beginning of the scenario, and adding Bulgaria's leader list to the existing one (so that it became, in effect, the Graeco-Bulgarian Empire

), worked out very well.
Rome and Athens are only 80% infrastructure in the historical scenarios, so it's not unreasonable if Constantinople is only 80% too. Or, like Venice and Milan, it could be 100%

. It should definitely be better than 60%, though. I've found the easiest way to mod infrastructure is in the country.inc files:
# increase Constantinople's infrastructure by 20%
province = { id = 409 infra = 0.20 }
Historically, the Arabs conquered right up to roughly the modern Syrian/Turkish border within a century or less of their expansion out of their peninsula, and then that border stayed stable for several centuries, until the Turks came onto the scene.
I'd like to keep all the existing tech teams, partly because sometimes I need two similar ones at once (especially OASU/SPAP) and partly because redundancies make the mod easier to, well, mod. For example, I play without the Spartan Officers' College, which wouldn't be as easy if the various weaker researchers didn't exist. On the other hand, some of the weaker ones could certainly be tweaked. Ideas?
For my own play, I've changed certain events to give the Empire lots of cores in Crimea, the Ukraine, Georgia, Armenia, and Russia rather than in the Middle East. Given, among other things, Stalin's repression of the Russian Orthodox Church, an Orthodox, Greek-speaking army would I think have been perceived as liberators by many in the Ukraine. In contrast, Arab muslims wouldn't have been particularly impressed by Byzantine claims of right to rule Arab-inhabited territories. The only place southeast of the RL Turkish border that I give the Empire cores is Lebannon.
Of course, while I find this "realistic", it's rather useless unless you invade the Soviet Union, which limits your gameplay options a lot, to say the least. I've compensated by giving the Empire lend-lease events if it joins the Allies, so your country grows economically either way.
The navy should be larger, but perhaps not much larger, since in this timeline the Empire was defeated by the Anglo-French Entente in the Great War, and the British had a habit of severely restricting the navies of countries they defeated in their peace treaties. I tend to toss in an old battlecruiser (the
Goeben under another name), upgrade the
Averof to an armoured cruiser (CA-0) (since that's what she is), and add a newer light cruiser and a few flotillas of slightly newer destroyers and subs. On the other hand, for variants in which the Empire is supposed to have been on the winning side in WWI, it should have a navy of similar size (4-5 BB-0, 7 CA-2) to those of Italy and France, as it has an economy of similar size to theirs and would presumably have signed the Washington Naval Treaty and been given parity with them.
Here's some other threads that people interested in this mod may find interesting:
A discussion of names of army units in Greek:
http://forum.paradoxplaza.com/forum/showthread.php?t=300971
Some Greeks discussing ways to improve the representation of Greece in this game:
http://forum.paradoxplaza.com/forum/showthread.php?t=279897
A very nicely written AAR using this mod:
http://forum.paradoxplaza.com/forum/showthread.php?t=281647