I did purchase one of the ShelterLogic tents as pictured in #6 above. I contemplated building a 2x? deck for it, but ran out of time and $$, so I secured it to the ground with the anchors that came with it. I did purchase a couple lengths of 1" pvc pipe to stiffen up the back side as well as the "door" on the frontside.
I have my pickup stored inside my scant 2-car garage (it's barely big enough for the pickup and a little of work space, as most garages that were built in the 70's were.) At least it's heated. I primarily built the Shelterlogic unit to store my "new to me" Mullins Red Cap trailer (pictured below), as well as my lawn mower and snow blower, since there is no room in my garage for such mundane things.
As to Idea #5 in pgerhardt's post above. Good idea! I erected mine by myself. The instructions says it takes about 2 hours. I spent the better part of 3 days doing mine. A little help would have gone a long way in reducing that time.