Our FAA Ops Specs criteria for a "Departure Alternate" is that the airport is within 2 hours cruise (still air) with one engine inop. If that condition cannot be met, then obviously takeoff is not permitted...until an airport within two hours cruise in still air (including the airport of origin) meets alternate landing weather minimums.
I think what you need to keep in mind is that a minimum visibility takeoff is not predicated on being able to immediatley return to the point of departure. I have departed many airports many times in weather conditions that precluded a return in case of an engine failure.