I guess I'm wondering why he wants it thick. For the weight? More warmth? Warm and Natural is flatter, but I like of the weight of quilts made with it. And Warm & Natural is nice and warm. Hubby and I were camping in Northeastern Washington last weekend and it was below freezing overnight and we were toasty warm in our sleeping bags with a quilt made with W&N over us.
If he just wants it fluffy, then a high loft polyester would be needed, but that wouldn't be very heavy and probably not as warm. What batting you use would depend on what he wants exactly.