A way must be found to make sure that it does well as an AI.
Why? The 'polynesian civilization' didn't do well in real life, if we're comparing it to the other civs in the game. They didn't do anything particularly important from a historical context, other than surviving for a long time in an isolated, completely disunited way until Western explorers eventually came along.
If this proposed polynesian civ tends to become a one or two-island state that collapses into non-aligned barbarian cities, from a CivIV perspective that is a pretty accurate depiction of the area's actual history (excepting the fact that the Polynesians were never really united enough for a region-wide 'collapse' to happen in the first place). I mean, what did the European explorers who came there during the age of exploration find? A bunch of disunited, hunter-gatherer tribes that occasionally fought with each other. Even one of the most well-known Polynesian civilizations, the Easter Islanders, managed to collapse without ever leaving their island. Trying to operate a government across a bunch of distant islets with only hunter-gatherer technology at your disposal is a losing proposition, and while it would be a nice challenge for a human player, I doubt the AI would be able to do much in that situation, even with UPs and such being used as crutches to prop it up.
I'm not saying they necessarily NEED to be a human-only civ. I just don't think it's worth altering the mod all that much in an effort to help make them more than what they were.
That being said, this is an RFC mod and historical accuracy is not exactly paramount. So if the Polynesians aren't going to occasionally settle in Australia or NZ or New Guinea or something, I don't really see the point in including them as an AI at all. You could just plop some barb cities on the islands in the area and you'd have the same end result by the time the Europeans arrive.
edit: and before people start piling on me for calling them 'hunter-gatherers', yes I am aware that many tribes in the area knew how to grow crops, and thus were not technically hunter-gatherers.