The bigger issue with multiple rings on a hub gear is surely going to be that your drive ratio will be outside the manufacturer's recommended range, which means you'll be applying too much torque to the hub, which means either the hub's internal gears or the anti-rotation mechanism will break.
e.g.
To prevent overstraining the hub, a minimum sprocket ratio of 2.35 must be used. With the available sprockets these minimum ratios are achieved by: 40/17, 38/16, 36/15 and 32/13.
The bigger issue with multiple rings on a hub gear is surely going to be that your drive ratio will be outside the manufacturer's recommended range, which means you'll be applying too much torque to the hub, which means either the hub's internal gears or the anti-rotation mechanism will break.
e.g.