One word: Warwick. To them, lefty is lefty, full stop - knobs, adjustable nut, truss rod cover, etc., all perfectly mirrored and not recycled from righty parts. I'm not aware of them ever having manufactured a hybrid of the sort you guys mention here, and I'm appalled to hear that that happens on other makes, especially on expensive ones.
I have a Bass Collection which is fine too, except for the upside-down truss rod cover!