G'day @Orangelane I have Poly (Polystyrene) Nuc's one National and one Langstroth also a Langstroth full Hive and 2 feeders.
I'm sure you could modify the Poly but it would affect the integrity I think and sort of defeats the warmth/cool aspect. Poly's are cheap enough if it didn't work you have not cost yourself a fortune. Suggest you try on a cardboard box first, work out what you want to do and have a practice. Nothing ventured nothing gained!
Personally I went for poly Nuc's as they are light easy and quite cheap, The Poly Hive and feeders because they are warm and I had seen some and they are pretty OK.
I'm hoping to put a Poly feeder over my wooden hive to feed if needs be in winter - the Poly feeder is integral and £20 to buy a wooden set up it is £10 for the feeder and then £20-£50 for the eek or super to go over it - pure economics.
If you only want for the cooling aspect you could always create a "Coolgardie" effect - Tub of water, hessian (burlap) and drape the hessian over the hives and the base of the hessian in the water - the "wick" effect of the hessian draws water from the source a wets it, the natural atmospheric elements wind, breeze, sunshine, means the water evaporates and "Cools" - This is the old Aussie outback fridge named after where it was created in WA.
I used this technique in summer to keep my Guinea pigs cool - simple effective and cheap
Hope that helps