I'm a huge fan of out side sun cages. I'm of the opinion it is the best way to expose your chameleons to UV rays. For me you cannot go to big with suncages as well. If you are worried about ants, if you have got a stand, put each stands legs in a bucket of water.
The main concern is as being outside the chameleons can be tempted to escape and nose rubbing and screen climbing can be a problem. You may want to look for plastic covered screen to build your sun cage with.
Here is my outdoor/summer setup. Made of PVC pipes, zip-ties, garden/bird proof netting. Added a 2x4 to the top with two misting nozzles. I can also hang plants down from the 2x4. The misting nozzles are hooked up with a line that runs to my inside/winter cage in the garage. When I move my cham outside, I just switch valves in my reservoir to revert the water to outside. Works, great all spring and summer. Also added a shade cloth on one side to block the sun at high noon.