Did you try to override DefaultPawn_MoveForward in config file?
As they are harcoded it just before read it, I’m not sure it will work, but you may try.
Otherwise, just add you own default pawn and setup your inputs. You have no choice, it’s a game setup and not Engine.
you may raise a Feature Request to have the DefaultPawn settings available in ini file and not hardcoded, but this is not the initial bugs that is now solved.