Good point. But ppl have tried vegan diets and have lots of negative outcomes. Such as raw vegans.
And for vegetarian diets, indians have lots of diabetes. But that is probably due to lots of unhealthy food.
You are right that a paleo plant diet could work. There is even a study in an indian journal about using a paleo plant diet to reverse or better manage diabetes. And they provided a list of protein and fat based meals.