Air bags are not the solution!
You can have a good hitch shop strengthen your receiver so that it can withstand the twisting stress (fore and aft) that a weight distribution hitch creates.
Check out this video showing that air bags don't help with weight distribution (but can only help to...
Do you have the heavy duty tow package?
My previous Jeep, a JKU Sahara, had 3.73 gears, and 4 speed automatic transmission. I towed a travel trailer from the east coast to the west, through mountains and deserts with no problems. However, the transmission did do a bit of gear hunting. Now...
Looks good. I would recommend at least one side view mirror. I use Harley-Davidson motorcycle mirrors which I picked up used for about $15. They fit into the top hinge on each side. (To make them a tighter fit I put a couple of layers of shrink tubing around the stem.)
The bottom of my top is about 50" from the ceiling. I have the freedom panels and other items stored on top of the Racor platform. It could be raised at least another 6" and if the stored items were removed it could be raised about 12 - 18".
The Audi A4 weighs between 3252 and 4079 lbs depending on the trim and model year. If you have the max tow package you should be able to mange this easily.
You should check the Audi's owner manual on how to configure it so it can be towed.
Why do you need to get all four wheels off of the ground. If you move one of the left side tires to the right side you may be able to get it onto a dolly and tow it more easily than trying to load it onto a trailer.