Customize user roles in Power BI service

It would be a nice feature to be able to add rules to existing service roles or to be able to create a new service role. Use case, I have a few developers that I don't want to be able to anything other than view and download the PBIX files in a production workspace. Adding more permissions creates potential issues with governance, but I would like for them to be able to download the PBIX files for developing or seeing how things work.