I've started two games at the same time in this new RFCE: Arabs and Byzantine
As both some bugs keep happening, and they're not from this version, they were present in Betas too:
Autosaves that happen in the turn that cities try to flip to a new civ when loaded cancel the flip as if it never happened.
The Merc system is really bizarre. Sometimes they tell me some mercs are available when they're not, even in provinces such as Egypt (it happened with both Arabia and Byzantium), where I had only Alexandria and surely I had more then the minimum culture necessary. Not once, but all the time it happens. The same way, the message that mercs left when there were none on the same provinces. It's like they come, keep some time there and then leave, but I couldn't hire then because they never showed on my merc advisor. And last not least, they come at a specific level, but when they appear on the map the level drops to 1 and the ups don't disappear. This opens the possibility for overpowering mercs ( I had one with Byzantine a Khazar Horse Archer with Medic I, Medic II, Strengh I, Drill I and after 2 battles it got to 6 XP, so I could put Withdraw I and II, only 4 XP left to get March and make this Merc the Overlord of my troops)
And the last one happens when two civs at war call you at the same turn asking something from you. The last example that happened to me: France was at war with Cordoba. The turn started and France called me to declare war at Cordoba. I agreed. Exactly after this Cordoba asked me to declare war at France. I negated. Then I was at the Diplomacy screen with Cordoba, even being at war with them (and necessarily they wouldn't accept a diplomatic chat with me at the same turn I declared war and no war move was made to make them reconsider the chat). I clicked "We would like to make a trade proposal" and suddenly there was no "trade proposal" screen, but the same screen as before with the options as I was proposing some kind of deal, but there was no deal. I clicked at the first option asking if Cordoba would accept my phantom deal and they agreed, stopping the war as if we had proposed Cease Fire. Same happened as Arabia when Cordoba asked me first to declare war on Spain and after that Spain came asking the same to me.
Besides these issues I was considering something about the last UHV of Byzantines. In my opinion it's one of the easiest UHVs on this game. If you could make Constantinople the most powerful city in 1025 (UHV1), and you could gather all Anatolia under your thumb (UHV2), UHV3 can be simply done by controlling the Ottomans and putting 100% of your commerce on the treasure for the rest of the turns (more or less a hundred years to make that).
But there is a way even easier to do that (even when you can't handle the Ottomans but you can survive until the limit year of UHV3). All my games in all versions of RFCE (excluding a bugged one long time ago that Arabia had more then a million gold) had the Papal states as the richest Empire in the world by far (with thousands of gold). But they can't fight any civilization in the espionage battle, losing easily even to the worst of them. Some turns of EPs directed at the Pope and a single spy is all you need to steal thousands of gold from him in a single move making you the richest and putting the old richest behind you. So what's the challenge in this UHV?