Multi-User Access control & advanced admin

We would like to have one company admin.

Admin uploads a universal page of content (images/links/etc), adds multiple users, and gives the users access to their specific page/post (but all users have universal content). The user can add their logo or images, but the text and other info is universal for all pages/posts for that user and provided by the company admin.

Example: Company Admin gives each business partner a page/post by category for other anyone to see. Think “dealer” search pages. The partner can add their logo and images, but cannot alter the rest of the page. When the admin updates the universal info, every partner gets the same content fed to the page. Partners cannot edit anything but their page/post.

Blog in Blog plug-in comes to mind, but how do we limit control of each partner to their specific content (cannot add pages, only edit their content – but not the company content fed to their page/post) the site to each user.