I've done quite a bit of AT section hiking, and I've used bivys for some. Haven't used a Ti Goat bivy; I'm using an homemade Momentum/silnylon bivy, which should have similar breathability. It's great October thru May, but in the summer it gets pretty sticky in there!
For these really hot hikes, I've been using a Sea to Summit sleep screen; pretty simple and at about 35 bucks, pretty inexpensive. It allows any cooling breezes in while keeping the skeeters and blackflies at bay. It also can be easily used in a shelter for bug pro; I also sometimes just drape it over me during meals if the biters get bad!
Along with Jason, I agree that some bug pro and a silk mummy liner are about all you need down south in the summer. Although I usually just zip the legs on my saharas, put on a long sleeve shirt, and crash! Except this year; I'm cureently planning a SUL solar AC! ;) It's gonna be a scorcher this summer, but at least my pack weight will be down; if the temp keeps rising, I won't need anything but my Steripen and a loincloth by August!