Good evening:)
I like your dreams:)
Alot of people around here have been building (I think we've talked about this before:) arenas that are covered, but then have canvas sides, that can be raised or lowered as the need arises. If I was building one, that is the route I'd go.
I've worked in enought barns to have lost the desire for a fully enclosed one for this area. If I moved to where the weather was more harsh, I'd want something different. In the barns around here, it seemed to me in the summer they had trouble keeping the stalled horses cool enough. Fans help, but can raise dust.
Becky
Here, if it's shady, it's relatively cool, and the cooling I've thought I'd need is just the breezeway of having the aisles go all the way through, and vents in the roof. We don't have too many days of penetrating heat.