Are you capable of making Byzantium playable? I've looked into it myself, but this programming business is beyond me.
It's certainly possible. The problem is that as far as I know, it would require removing a civ, and would take a long time to mod. An easier way might be to introduce Rome or Greece in the 600AD start as Byzantium. Though it looks like someone may have solved the problem. I might look into incorporating that Byzantium scenario, but to be honest, I'd rather finish up some of the modifications I'm already working on now first, since many of them are unfinished. I'll add it to the to do list, which already includes:
1: Reworking many of the wonders to accommodate the new ones Leoreth added. Sphinx, St Basil's, Dome of the Rock, and Temple of Solomon, are the one's that need it bad in my opinion. Also I want to find another way to restrict the Mediterranean wonders without the marble prereq (One big problem is that it slows Egypt and Babylon down since they need to hook up both marble and stone to start on early wonders.) Mostly done, but I want to play a game or to make sure it's balanced.
2: Civics. Leoreth did a great thing trying to redo the civics, RFC really needed it, since they seemed like the only thing unchanged from vanilla, but he's opened up a few new problems, like a secular theocracy and a state property capitalist system. I've got a few ideas on paper waiting to be implemented.
3: Map changes. I greatly modified the map a long time ago on regular RFC, but it was all world builder saves. I need to apply that more seamlessly than a sloppy world builder mod, maybe by making the map change over time.
4: Events. I want to add more events and unit spawns for each civ, (like making Hannibal appear in Northern Italy in 220BC), and maybe a unique quest for each. The first three are all half done, but this is only barely started, but will be probably the most sweeping change.
5: Then I'll see about adding Byzantium, and probably the Celts too while I'm at it.