Sweaty back is just part of the experience for me. A mesh-backed seat helps some, and I suppose you could adapt one; but it might not work as well as what you've got. I don't know for sure about your current pad; but the most circulation you'll be able to get with a hardshell seat will be with a Ventisit pad. It's an open mesh, with almost no compressibility (just enough for shock absorption.)

My hardshells all have Zotefoam pads, which have almost no air circulation. It was 91F for last evening's ride, so yeah I got sweaty.