Theres a video on Youtube somewhere , of an older Italian guy Stick Welding a derailluer Hanger on a Colnago , yes a stick welder . (i couldnt find it)

Ive rewelded missing and cracked Hangers several times with good results , Its not too complicated . I used a Mig welder and preheated the dropouts .

Practice on a crappy frame first , cut it off ,bevel grind it and reweld it . I bent the entire dropout before the weld cracked . Its fairly easy .