Yeah, it's supposedly doable. NAA had something like that worked up for the F-108. IIRC, that had a door that retracted into the fuselage. Too, the YF-12 launched from supersonic speeds and extended the missile on a trapeze through outward-opening doors. You almost have to have the trapeze to get the missile clear of the boundary layer, and to make certain the seeker has a proper lock before launch. At launch, the missile gets kicked down and away to fully clear the aircraft before ignition.