Okay, longtime player, but I haven't posted in a long while. (Not since, I believe, a related request that got the copper on the tile south of Constantinople.)
First things first, I love this modmodmod. It's awesome, and has almost everything I wanted in the original RFCE (which is still amazing). Anyway, to brass tacks. I might be the only person who still loves to play the Byzantines (call me sick, I know) but I happen to be a big fan of the Greeks. I'm a huge fan of the inclusion of Rum, and the massive barb pressure: plus, it's great that I now have a compelling reason not to keep Egypt. At the same time, I've think I might have a solution to what I see as three balance issues in the area.
1.) Turkey doesn't become the juggernaut it should be.
2.) The Holy Land is much more boring than the intricacies of Europe, and the Arabs don't quite become the power I'd like to see anymore.
3.) The actual Byzantine game can be annoying to the point of not fun, if you lose a couple odded barb battles.
I'll address 3.) first, because they all sort of flow from my fix for this. The crux of the problem with the Byzantines right now is, even though Anatolia is less fertile (a change I am highly in favor of) the AI still doesn't lose enough, and making it any harder on the human will render the civ unplayable for anyone who doesn't micromanage the bejesus out of a huge empire. Mind you, I pretty much do, and I even reloaded once or twice out of frustration. To fix this, I think the first step is to strengthen the Byzantines by lowering the production and/or research penalties to 75-90% of what they are now. (After hitting 1080, I'm thinking only 80%-90%, and probably the latter of those. But there should be something, I just couldn't build enough swords/archers, and it took 9/10ths of eternity to research vaunted arches.) That'll give humans a chance to capitalize on the early game position. Additionally, I think it would be worthwhile to put either a crab two tiles south of Smyrna, or a fish two tiles south of the wheat next to Smyrna. The latter would give the human player the opportunity to found a city in the Tralles/Halikarnas region: either resource would strengthen the future Ottomans.
But how to ensure AI failure? One way is to make Rum into a better power. This one is three steps. First, enlarge the Seljuk flip to include Caesarea and central Colonea. Second get rid of the flatland desert in Colonea, replace with plains: throw a cow/pig there, and spawn a barb city there in 850 AD, that the Turkish will get. (RFC:SOI has a name and location, I can fetch it if you want.) Third, make the Rum UU a 7 strength, no-iron-required lancer replacement, as opposed to an HA replacement. Sort of like a proto-Huszar: a 3-move horse archer (keep Turkomen HA name and the 40% withdrawal, maybe add collateral damage? 10% vs. Heavy Cav? No city attack penalty?) If that's too drastic, I'd at least suggest changing their modifiers to make them slightly more productive. The other way to kill the AI (and challenge the human) is to strengthen the barbs in Colonea. They were a huge problem and a challenge when I had to counter a ton of HAs and Axes with a few Archers and Swords. But even with the Byzantines production and research penalties, I simply out-teched them. Since they couldn't kill my promoted units, and I eventually had crossbows, there wasn't much of a challenge. I'd suggest giving them swords and Turkomen HAs/or Lancers @ 750AD, and heralding the arrival of the waves of Turks with even greater barb pressure at 980-90 to 1050-60.
To address 2.), I think Jerusalem should provide some kind of permanent stability or gold boost, in the form of a pre-built Stephansdom-like wonder (Maybe called Temple Mount, after that's renamed: +5 stability?) or a Jewish shrine. To make the Arabs rock again, stick a fish in the northernmost tile of the Gulf of Aqaba (or turn it into a floodplains desert, if that's too much), leave the clams where they are, and pre-build an indie Aqaba one square to the east of the tip of the gulf either at start or by 600AD. (I think the dynamic name is Ramleh, but the spots N or NE of the Gulf are worse - and Aqaba is slightly on the East side on googlemaps, anyway. ) As an aside, I'd also avoid the auto-war on start for the Arabs. I'd like to gift them the Holy Land to save my stability, and since I wasn't given the option, I gifted it to the Lombards instead (tres historical, no?) Either way, with their warmap, if their attitude modifier is low enough, they'll DoW AI Byzantium.
1.) Ah, the Terrible Turks. They are troublesome. To reiterate, I think giving south-western Anatolia a little more off-shore food would help pump them up. But I really think the problem lies in the inability of the AI to effectively use the Turkish power or UU. And then I realized the problem: they should be switched. If the power was "Siege units start with City Attack I & II" and the unit was "Musketman replacement: Janissary: 11str, 1/2 move, 25% City Strength (or 25% City Attack and 2 first strikes)," we'd probably see them better able to both take and keep cities, even if they don't get more starting units (which I would consider).
I've got more thoughts on the Scots, Spanish, Prussians, and general MAF-avoidance measures, but I think this post is long enough. Thanks much for the brilliant addition to CIV IV, and happy modding!