Rear wheel with disc brake & 40T sprocket

I found out I have to register the bike I'm building as a "low powered scooter", but the Dept. Of Revenue won't register it if it's on "a bicycle". So, I'm building it without a bottom bracket, cranks or pedals, chain, or rear cog. That renders it only a "low powered scooter" and a non-bicycle. Now there can't be a coaster brake though, and I want to use a disc brake. So, I need a rear wheel with a 40 tooth sprocket and adapter on the left, and a disc rotor mount on the right. I'm brainstorming and searching the internet for the right setup. I have a steel wheel 26" x 2.125") with a coaster brake hub and 12 guage spokes that I was going to use, and I want something solid like it. Does anyone have any ideas about how to build one?

Another option I've considered is using the coaster brake wheel I have, removing the brake arm and cog. Then it would be a free spinning wheel without any way to pedal backwards engaging the brake shoes inside the hub. I would have to use a regular caliper brake then, but I'm mainly relying on the front disc brake for stopping power anyway. I could mount the 40 tooth sprocket to the hub with an adapter.

Would the coaster brake hub stand up to this kind of use?