I think that before I embarked on the whole quilt I would do a little testing. (it's something I've wondered also). I'd cut two equal sized pieces one of homespun and one of cotton.. then wash, dry, press and re-measure to see if they shrink at the same rate.. this has been my biggest question. Also I'd test them all for colorfastness.
If the tests come out OK.. I say go for it. Many art quilts use multiple types of fabrics.