Exactly my thoughts.
It definitely can be done, and it would be great to have the Dome properly cooled to give a central place to cool off and eat, shop etc in the height of summer, even just as you walk through having queued for security in the sun. Probably wishful thinking though as with this year's highlight addition being a bouncy castle, it's probably at the bottom of the priority list for investment. It would be quite a large system to cover a space of that size too.
Even the toilets at DLP are heated/air conditioned all year round though! Little things like that make such a difference. And when late October Fright Nights comes around and its 5 degrees outside.. there's hardly anywhere around to warm up either!