With regards to attack / backs coaches, if we want someone with some kind of Wasps background, then Rob Howley probably has the best CV around.
Realistically, his competition would be Kinga and Walder.
Walder had a great season with Newcastle, but then a relegated season
Kinga was great at Clermont, and it looked good for a while at saints, but then it ended badly (not necessarily his fault)
CV wise there's no contest, although Rob's experience of coaching at club level is limited