I've seen a bunch of these kinds of canoe tents on Pinterest. If I can figure out how to move photos from there to here, I'll do that. Some are different designs.
I have a couple of times thought I was going to have to sleep in the canoe...mostly in marshy areas. Always lucked out at the last minute by some soggy but stable ground. It seemed to me it would be really uncomfortable contorting oneself around the gear and thwarts and seats.
I agree that probably the best use is to go down rivers where no camping is allowed on the banks. Or in Virginia I think it was, one could paddle down the waterway, but the bottom was private land and you couldn't get out of the boat. I was looking at a pretty run somewhere in the Midwest, but you had to run it all in one day because there was no camping. Juniper Springs in Florida is no camping. No even getting out of the boat.