many of the (big winners) beautifully machine quilted quilts are quilted with wool & w/n battings together- you can certainly do that- as for being too warm---i don't think so, warm & natural is a pretty 'flat' batt, wool gives some nice loft- gives quilting stitches great definition. both fibers breath- i have a quilt that has wool/cotton batting, regular cotton top, flannel back- and it is the one that we even use during the spring & fall- i add a blanket to the bed in the winter.