At least for single entries this is good enough also to pass from CLI, e.g. -Daether.connector.http.headers.myrepo="custom-auth-header=customauthvalue". Multiple entries are a pain indeed, but should rarely occur. In any case this is better than before, IMHO. I cannot think of a good solution for multiple entries for CLI or do you have any proposal?

The only thing I can image is that String will contain a local path to a proprties file. But I really would put this issue aside until someone really complains that this does not work.