A useful feature for more information on the user is to have a unified role field under the user in place of the separate is_admin, is_viewer, and is_guest to a unified role field where not only these three existing roles of the user can be fetched but also the member role, and any custom role that the user falls under. Intuitively instead of returning a Boolean value for the role type the name of the role would instead be returned.
What is the use case for knowing the role name? With custom roles how would you know what limitations to place on the user?
The boolean values exist primarily for use in the {me{is_admin, is_guest, is_view_only}} query. This is for getting the current users permissions for your app - with those three boolean values you can easily control what a user is allowed to do in your app.