This interpretation is however only possible if one has foreknowledge of Gibson's Catholicism. To view the movie as self-repesentational, I think one should subtract that. (I state this with all due respect to and in full recognition of what the cross symbolizes in Catholicism, Catholicism, and Gibson's Catholicism.)
Also, the movie does destroy the "Noble Savage" myth. The Mayans were "uncorrupted" by Western Civilization or Christianity, from the liberal point of view, yet they engaged in horrendous and evil acts.
No, the noble savage motif (in my opinion) only applies to the jungle tribal Mayans, not the "civilized" Mayans. The jungle tribe did not practice those evils. (NB: by this time in history, I believe historians generally concur that Mayan civilization was in decline and Mayans no longer had a central uniting government or ruler. They had reverted back to city states or back to subsistence lifestyles in the jungle, depnding on the time and specific location.)
Western Civilization is a clear improvement on what the average Mayan was enduring at the hands of the witch doctors and other Mayans.
Mmm, well, just to take the devil's advocate view (apologies for the pun), the peaceful co-existence of the jungle tribe with their native ecology is shattered by the civilized but evil, industrialized Mayans. Without overly spoiling the plot for any future viewer-readers, the movie does depict that the peaceful, environmentally friendly jungle Mayans had a chance to embrace Catholicism and Western civilization, but in the end, they declined. So the ideal of the Noble Savage is upheld, at the expense of both Mayan and Western civilizations. The notion that "Western Civilization is a clear improvement on what the average Mayan was enduring at the hands of the witch doctors and other Mayans" is IMHO-- as much as one might be inclined to cheer it and/or Gibson-- a projection onto the movie rather than the main message that the movie itself contains.
In the final analysis, the only person who can accurately represent Mel's artistic goals for this movie is Mel himself - and I think Mel knows that a large part of his last movie's success was from the church community.
That is why he shows Jaguar Paw near the end, on his knees in the sand, facing the Spanish with their cross. Mel has put other religious symbols and sounds from the Passion, as other posters have noted, in this movie such as the withered baby from the temple sacrifice scene - the symbol of Satan being present in the crowd. Ironically, to gain acceptance for the movie from the Hollywood crowd, I believe Mel may be touting the movie as being about the environment instead of the depraved (sin) nature of man.
Again, you may be right in your interpretation - perhaps Mel will have an interview where he discusses these issues about the movie.