Rich, the problem you might find with that is when you buy a bag of 'cherry' it's usually 70-80% oak or alder and 20-30% cherry in many brands. The same ratio often applies to all single flavors in those brands. Many or maybe most of the special blends leave out the base wood and give you 100% flavor woods in advertised or secret ratios. CookinPellets and Lumberjack are the only I've found in what I've tried that offer 100% single species. Lumberjack also does oak/flavor though too, so you have to shop carefully to get their 100% flavor bags and not a 70/30.
So if you mix Traeger Cherry, Hickory and Apple, you're going to likely end up with 70% oak or alder (depending on if the bags originate from east or west of the Mississippi), 10 percent cherry, 10 percent apple and 10 percent hickory.