A user can administer the privileges of some schemas only?

My coworkers are developing an application and they want to create a "manager" user, and three different users with objects of its own, let's say commercial, financial and tech.

They want the manager user be able to create app users (which would be DB users as well) and grant read and write privileges to them on the other three users' objects. They don't want to issue the grant command "with grant option" individually for each one of the three users objects to the manager for he can transfer them to the new app users, they are looking for an easier and quick alternative.