the thing is, even with another leader, you can push the happy limit with the use of the slider in a cultural game.I know this is an old thread but...
I'm surprised that no mention has been made of the hippodrome, which is surprisingly good for attempting cultural victories in the late game.
This is counter intuitive I know, because the UB doesn't allow you to select artists. But, setting the culture slider to 30% will give you another six happy, you're bound to have horses and the hippodrome without modifiers should give you another 3 smiley faces in your cities. More than enough to manage caste system even when other civs have adopted emancipation: which provides unlimited artists. Put it up to 100% for the final push and unhappiness from any source isn't even going to be an issue.
This is never an issue for me.