The histrionicus you describe sound interesting. The big Oophaga are pretty rare these days, so hearing accounts of them being kept are always interesting to me. Did they ever breed for you? I've never seen an auratus like you describe, probably one of the many lost to popularity swings. There aren't many keeping the less common auratus now, even the Costa Rican greens aren't offered for sale much. Thanks for the pictures!
The 80F heat ceiling has a lot to do with people keeping totally sealed enclosures. They often experience 90+F in nature, but they take advantage of evaporative cooling and find cooler niches within their habitat. Mine survived the high temps I think because all of my tanks are vented to fresh air. I think chytrid is killed above 85F or something close to that, but I've never heard or read of chytrid as a proven reason a collection was lost. New imports sometimes test positive for it, but they are treated with antifungals while in quarantine. The crawfish as a vector is still being debated, but many amphibians are unaffected by the fungus but serve as vectors to keep it going during dry seasons or after it wipes out a specific population...red eye tree frogs, green tree frogs, and I think even bull frogs can be vectors.
As long as the greenhouse was escape proof and the frogs had access to sufficient food, I think they'd do great in one. Species like tricolor, the highland morph of anthonyi, H. azureiventris, and many of the riverine Ameerega come to mind as candidates. The Atlanta Botanic Gardens has E. tricolor free roaming in their cloudforest exhibit.