The whole idea of a Wordpress multisite is what you have described. The access delegation can be done with a plugin.
I am a senior developer, worked in many companies. Now for obvious reasons, entered into the freelance arena. I have not just set up multisite projects, I have also helped companies troubleshoot the issues on upgrading their multisite setup. The success of a multisite is also dependent upon the hosting provider. Though WordPress and WordPress multisite are similar, a developer experienced in multisite will be the ideal candidate for your project.
The amount I mentioned is just for reference. Would like to connect with you and get clarity before proceeding.