There doesn't seem to be an article on either of those pantheons. I'm sort of curious on how the powers of those pantheons would fit into the planes as a whole and where would they be?
I know there's a few mentions of Quetzalcoatl in a few supplements, as him and Tezcatlipoca recently got a short write-up in Dragon magazine. But not much in the way of mentions of others like Tlaloc, Xipe Totec, Mictlantecuhtl, Huitzilopochtli and others.
And to my knowledge there's never been a mention of Afro-Caribbean powers in D&D anywhere. Yeah I know they sort of are considered as just powerful spirits as Loa, and are a mixture of African Gods with Catholic Saints. But where would you fit Baron Samedi, Damballa, and the rest of them?
When you speak of the Afro-Caribbean powers, bear in mind that there were originally gods native to Africa, with their own identities, myths, and rituals. Their worship was vastly bent out of shape by the conditions under which their worshipers lived in the New World, causing a mixing of ritual and mythical elements with the dominant religion of the slavers, i.e., Christianity.
I would actually make the African gods and the loa separate entities, or almost separate. The original gods were much like any pantheon of spirits for Stone Age tribes, perhaps with slight variations in names or worship across large groups of related cultures in the region. In D&D, they would possibly be one of the oldest stable pantheons in existence, serving primitive tribes in low-tech areas of various game worlds (albeit possibly an area that was once one of the more advanced in historical technology, leading to very raw sorts of "dungeon" ruins: ancient gathering places, forest refuges, cave systems, and the like). Pardon the characterization, but typical worshipers in d20 would be "barbarians" with, of course, clerics of their own.
Worshipers kidnapped from their homes lose touch with much of their religious community, including their holy men, sacred places and communal rituals. If a large-scale slavery movement did not happen in a particular world, perhaps a great disaster cut off a large segment of the base population from their historical home and they had to go wandering. Under such conditions, several things might happen.
First, the gods might continue to look after their children, by splitting off aspects more suited to the harsh conditions of their new lives. In this case, the loa are simply the African gods, but with different names and styles of worship.
Second, opportunistic spirits might seek the lost populations' worship. This would make the loa a wholly new pantheon -- one that has stolen the mantles of the people's original gods, devised more suitable new worsip rites under the guise of adapting old rites to new conditions, and is now collecting energy from believers. At best, they might be self-involved neutrals, and at worst, their gods of death (Samedi), war (Chango), and the like could well be evil deities. On of the literary staples of voodoo is, of course, the raising of zombies, a necessarily evil act in D&D. (In real life, this might have been the traumatic experience of taking a paralytic poison followed by being buried alive for 24 hours, leading to a will-broken obedient servant... but it's not like that's less evil.) From the Outlands or the Lower Planes, this pantheon might seek out primitive tribes in desperate straits and offer their religious guidance, supplanting their previous gods and gaining a lot of devoted worshipers, but making a lot of deific enemies along the way.
Third, the loa might be aspects of the dominant religion of the region -- the captors, if it's a slave movement, or the native of the region to which the castoff population has been thrust, if it was a natural disaster. Legba, god of crossroads, might be an aspect of Fharlangn, Erzulie a wild aspect of Ehlonna, or Venus, or another goddess of love. Elements of the original powers' worship would have crept into the rites, mixed with the forms of the old pantheon.
When talking about the loa, it's flavorful to also consider the magic of voodoo. A houngan, a practitioner of this magic, considers himself an intermediary between spirits and humans, and thus the "Spirit Shaman" from Complete Divine could make an excellent base class to describe this profession. C.J. Carella's Voodoo: The Shadow War is an excellent source for material on the loa and an interpretation of those spirits, and magic strongly based in the real-world traditions of voodoun. It uses GURPS mechanics, but it would not be at all difficult to convert the spells listed there to a d20 spell list that woud suit the flavor of a houngan perhaps more than typical cleric spells. In keeping with real-life magical traditions, houngans don't claim to be able to throw fireballs or whip up a storm on the instant, or even generate a ball of light; however, they do insist they can bless, curse, peer through time and space, heal many ailments, command spirits, exercise uncanny authority over the weak-willed, give orders to nature, erect protections of various kinds, and otherwise possess a spell list fully as useful as that of a standard cleric.