You know, thanks to your goading, I've now gone from joking to semi-serious about this idea...
If I do do this, I think it might be a good idea to take the runflats out of the tires to cut down on the weight. Better to make the tires able to spin to move the sofa or keep them fixed? I'm wondering if a futon could be hacked up to be adapted to it... Those large areas over the tires, near the turn signals, do lend themselves to some cup holders... Hmm, so many design considerations.
Well, the tires and hood aren't going anywhere so this might be a project best left for Springtime.
I think the sooner you do it the better lol. the tires should spin so you can roll it where you need it keep the run flats never know when your couch might get a flat.