Shane Howarth is to move on from the Club after a season, having decided to move out of London for family reasons.
Jones will step up and take on an attacking coaching role, and Davis, who joins at the start of pre-season, is set to lead the defence.
Young said: "We are sorry to lose Shane who has done a good job for us this season and we've reluctantly released him from his contract after his requests, due to his family wanting to move out of London. Stephen has already had a big influence in our attack this season and I am very confident in his ability to step up and carry on where Shane has left off.
Brad Davis will also be a very good addition for us. He's an excellent coach and is highly rated by the players who have worked with him and I think he brings a nice balance to the coaching team giving us a much stronger focus on our defence."
Davis is a former rugby league player who spent over six years coaching at Bath.
He said: "I'm excited to have the opportunity to join Wasps and to work with Dai and the team in helping them to achieve their goals. It is a squad full of huge potential and they have played some great attacking rugby this season so I'm really looking forward to working with the players to strengthen their defence so that we can compete and win games consistently at the highest level".