Custom PowerBI Roles

It would be great if a PowerBI capacity administrator could use custom roles for workspaces. Admin, Member, Contributor, Viewer is not quite granular enough. In our case, we would like to grant a select number of individuals the ability to promote content through a PowerBI pipelines without granting them full "Member" access. The ability to use "Contributor" with the ability to promote content through the pipeline is one example. having the ability to use custom roles would really help.