I'd like a total re-imagining set on a world in which the major races - humans, Vulcans, Klingons, Romulans, and assorted mongrel tribes - all evolved on different continents, none connected by land (except the Vulcan/Romulan ones), so they have to sail around to interact/fight/explore.
So basically a sail-powered Rome
/Game of Thrones
type show with the Trek
races, and without all that pesky enlightened humanism stuff. (Not that I don't love that about Trek, but I'd like to see this too.)
... Or, a Mirror Universe show, picking up from where "Mirror, Mirror" leaves off. It could take inspiration from the background events of Shatner's Mirror trilogy, but the main characters should all be MU ones, and the very existence of the Prime Universe a highly forbidden urban legend few if any really believe in.