Add user management to workflows

I know that the workflow module/app/engine/whatever we calls it, works on file level. However it would be awesome if we could expand it with an app or so, to also include users and groups.
As access to apps can be configured on group level, it would make sense to delegate administration on group level, based on a request or something. It could be as simple as just requesting access to a file, can trigger an approval, which then in the workflow engine, can be configured to assign a group for a user, if approved. It goes beyond this, as file and folder access can be granted on group level aswell, hence it would be a powerfull addition to Nextcloud, which could bring a huge enhancement in reducing potential admninistrative overhead.