Instead of the air bags and shocks, you might want to look into the Timbren SES system. As opposed to the air bags which require maintenance (airing up for loaded, airing down for unloaded and finding the right "air pressure" for a changing load; your trailer won't weigh the same each trip nor will the weight distribution be a constant), and shocks that may or may not help. Air bags and the shocks will also affect the unloaded ride of your GC when not towing.
The Timbrens replace the urethane spring bumpers with a polymer that has "progressive" support; the more you load them, the more suspension help they provide. I run them on my truck, ran them on my Commander (when I had it) for the extra control they provide. The beauty of the Timbrens is that when the vehicle isn't loaded, they don't come into play at all as they ride off the axle until loading brings them into play. They help with sag, off camber tilting and rebound control. I won't own a tow vehicle without them. They take mere minutes to install and once installed, you can forget about them. No maintenance, no adjustments, just help when the load needs it and it won't affect the stock ride of the vehicle when no load is present.