camp,
some airports like kin, lub, kalemie have RNAV approach pubblished on Jeppsen charts..it can be usefull..but not all the airplanes here are RNAV approved.
btw Goma has got only a VOR (as Mobutu said, intermittent) , 6° angle between the final course of the procedure and the rwy orientation and not even on the centerline..
many operators use to do what you said, especially approaching bush airstrips, creating their own procedures based on the threshold coordinates of their garmin...