Well, you could just swap out your chainrings on the double to get you into those lower gears. You might not need the tall gears for loading touring. GEt two smaller chainrings, you would be surprised at the spread you can have on them in a compact double set up. Make sure you have your lowest needed gear, I bet you will not feel cheated with your highest gear when touring loaded. Touring is, after all, about enjoying the trip? This would be less expensive and more easily reversed. One ring to climb, one to cruise, what more would you need?