I'd ditto the filter idea. You don't want to add dust/pollen/bugs to the mix inside there. I assume this is for a foam insulated spa? Thermostat's a good idea, but if the outside's air's hot, would it help too much? 80 degree air's still better than 100-120, I do suppose...
As was semi-mentioned, you may want to use two fans: one for inflow at the bottom, and one for exhaust at the top, with filters on both. Be sure rain and other (ground) water can't infiltrate either. (Nothing's easy!
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Hm, also, may want to run this by the dealer or manufacturer. Don't want a warranty claim to be disallowed because you 'modified' the factory configuration. You never know.
Bottom line, however, heat does affect electronics, but only if they're not designed for it, and I'd expect the control panels and other parts in these animals are made to bake in 120 degree heat all summer for years. This all may be a tempest in a teapot (sorry..).