It has to go into the car so I can lock the car up during the day when I am skiing. The tent will go on the back of the car, enlarging the interior space. I do have one of the doors that open up, but I have built a platform that extends the bed to be long enough for my 6' 2" frame to fit. This will leave the rear hatch propped open and unless I can make a suitable tent to close it I suspect quite drafty. My local area has a season pass for camping in the lot so it won't be a big deal if the subi looks odd. However thieves are always around, so I have to be able to lock the car up while I ski, which means moving the tent to the inside of the car.
another option is the seat extender. It's typically used to give more leg room to taller people (making the seat go back farther) but I believe it can also be used to make the seat go farther forward. Could be just the thing so you can sleep with the hatch shut. https://www.amazon.com/dp/B00ECVH24A...sert-amazon-20
I think the best option is to keep everything contained like powdork is saying. If you have a 4 door it shouldn't be a problem with the passenger seat forward. The tent idea sounds cool but will probably be a huge pain in the ass when it gets wet. Same problem with campers that have the soft pop outs, fucking awesome until you have to put it away wet and deal with the mold.
The only way this could viably work IMO would be to somehow drape it over the roof of the car during the day. Just close the corners in the doors.