One variation I was thinking of was to allow huts on the lower difficulty games. Removing the barb requirement on the higher might be might a good way to balance that.
I like this at least for the space and cultural games. I completely agree with STW about the barbs on deity.
I find that Religious victories seem to be pretty easy considering that most people should be able to win it at high levels.
The ease of Religious victories dramatically level the playing field and will make it easier for lower level players to be competitive. As you say, they are easy, so why not make it the 11th game (with a diplo game as the 10th).
I would like to see feedback from other people too. This is not Shulec's Challenge III.