It sounds like an interesting experiment. In an Indian curry, yogurt can serve several purposes:
1) Marinade. The acidity can tenderize meat (sometimes to excess), but also helps deliver flavors to the flesh. Will a coconut yogurt behave the same?
2) Thickener. This may depend on what coagulates coconut yogurt, and whether it holds up to heat. As a first experiment, I might suggest adding the coconut yogurt after removing the dish from the heat
3) Souring agent. Julie Sahni's "Classic Indian Cooking" stresses how important sour flavors are to Indian food, whether from tomatoes (and many other fruits, often dried), tamarind, yogurt or the occasional vinegar. Is coconut yogurt as tart as dairy?
What is patriotism, but the love of good things we ate in our childhood?
-- Lin Yutang