@Nanocy: There's alot of happiness-causing stuff already; we don't want combating unhappiness too easy, do we? There's, BTW, already a Royal Burial small wonder.
An issue I forgot to mention in the OP that nobody's commented at - the only way to get cities bigger than size twelve is building one of a number of Great and Small Wonders in them; I thought this was a rather neat idea - do people agree?
I was also thinking of removing the Defense unit from Tuxtla; this would make fighting the Mexicans a bit more rewarding endeavor for in particular Toniná (which tends to get bet up by the Mexicans, in my tests at least), and would allow a Maya player to control the entire upper Grijalva valley.
If I do this, I'd have to move the Green Obsidian resource there to somewhere at the western map age; the stuff really comes from central Mexico, and a Maya faction shouldn't be able to control it just by seizing Tuxtla.