I really like what you’ve done, but Kernow is the Cornish name for Cornwall, if you were to call Devon that too it would piss off both counties (who aren’t the best of friends, take it from a Cornishman 😅). Devon wouldn’t want to be named what is a Cornish name and Cornwall may not want to share it, so may I recommend something based on Dumnonia, the old name of the Celtic kingdom which contained both Counties? It may be a less inflammatory name choice.