Well, forts affect movement. If they are free - it isn't hard to delay an enemy attack with decoy forts. The AI is pretty dumb and will just attack forts for a few years while you build up a defense for the cities. The AI also has a habit of spamming watchtowers at the early part of the game. At 1,500, when was the last time that you spammed them during the first 20 turns? Heck, even at 50 mnai I almost never put up watchtowers. It isn't as though they buy time to allow you to intercept anyone with an army. Not to mention, Spies are much more useful.

As for slingers - I disagree with them having AP, but it doesn't matter. I like my slingers, you like yours.

I wouldn't mind giving many factions variety to better reflect their Gods, it was just too much of a hastle - so I gave them all one set which I felt was roughly balanced. Though, I find myself only using 3 of the temples... a big part of that is because the benefits from the other 3 temples can be achieved by the myriad of other buildings available (happiness, law, pop growth). There is a good chance that I'll end up axing some of the other buildings which will increase the usefulness of those temples.