I have a positive feeling that the espionage system will grow with time (mods + devs).
As for religion, I'm probably not going to found one in the game I'm playing. Playing Persia, emperor difficulty, on large map, 22 civs, 25 CS, Epic speed.
I'm on turn 143 and I only have 65 faith. Haven't been able to focus on it though. Lots of early skirmishes. I have had to play aggressive militarily because I'm pretty much in the middle of the continent--no ocean cities. But, I've had my eye on Ethiopia's capital for a few thousand years because it's gorgeous, it's on the coast, and it just happens to be the holy city for christianity. I took his second city in an early war and I've been trying to keep him pressed by paying people to war with him frequently. He still hasn't managed to replace his second city.
So, while I haven't focused on founding my own religion, I nonetheless have been focused on getting one. My military is top notch, my tech is buzzing along, my three cities all have great infrastructure, and my capital is rocking with 2 wonders--great library and petra. The Petra is incredible in a city with desert around. With Petra in my capital, I'm putting out 34 production, 25 gold, and 20 food per turn, at population 7 (in golden age right now).
My second city (the one I took from Ethiopia) is about to start building the national university. My third city is pure military and strategic defense, but it's production is complemented by gold, wine, iron, and horses.
I have lots of gold around my 3 cities. I shot out for mints for my gold, which I just got built in two of my cities. Plus, I've just begun my second golden age (back to back), which is perfectly timed to thwart this massive assault by mongolia.
So, once i've dealt with mongolia, and now that my gold count is up, I plan on supplementing my military with a few cats to go take that religion from Ethiopia! I'm assuming religions can be conquered, yeah?
Anyways, fun game. Loving this expansion. This is the feeling I used to get playing beyond the sword, but this is better. First time I've said that. Feels good.