I have thought about something like this for my Axis as well. I think if installed snaps or hooks on the the Drivers side you could attach a mesh material (you see this on some RV to block the sun.... its attach to the awning when its out). Plus it would allow you to see out the window and let more air flow in the RV.
I ended up tinting all my windows with cermic tint. They have a "Clear" tint (well 15% tint) that you put over ALL of your window - even the tinted ones (and including the front windshield). This rejects a ton of heat and UV rays (keeps interior looking like new longer).
Do a search on Cermic Window tint on this forum.
Plus there is many tips and trick to make your exsisting AC unit cool better so do a search on AC cooling as well.
2017 Axis / 25.4: Big Foot Levelers, Aims 1200 Watt inverter, Ceramic Window Tint, Full River AGM 6V batteries, Front Hellwig Sway bar / Rear Track Arm, Safe T Plus Steering Stabilizer, PD 4655 converter, Hard Wired Surge Guard, WEboost + WiFi Ranger, LED Headlights/Driving lights, TPMS, Surge tank, Tornado flush, Viair Compressor