I have a background in greenhouse construction, and have built the so-called "Chinese" model in Texas back in 1980 and more recently.
Your thought path and mine are parallel. Cooling is primary for me. The mass in the water has to been very beneficial. I am designing my raft beds, sump and fish tank out of concrete to introduce more mass. I will use "Thoroseal" to waterproof the concrete or CMU so that I can avoid using plastic liners. (Just can't wrap my mind around plastic) Since complex systems tend to fail, I am leaning away from Phase Change Materials and heat/cool tubes but the jury is still out. First greenhouse to be 48' x 32' x 20' tall.
There is a solid roof on the North that you can walk on to make putting on the plastic and 60% shade cloth safe and easy. I'll have 1 media bed 48' x 3' ; one raft 42' x 6' and a sump dug into the ground. Fish tank to have view window. About 1000 gallons (+ or-).