Pro Sites and/or Membership2 and/or User Role Editor?

I'm building a multisite network as described below. I believe the organization is very similar to EduBlogs. I'd like some help to identify the right plugins, and high-level guidance about how to setup. This request is somewhat similar to the other recent topic here. I'm looking into plugins recommended in this forum but I still need ideas about how to navigate where my structures are different from common WP structures.

Visitor roles are read-only and have access to common network site pages and posts.

A Visitor can register to create a Member role/account on the network site.

Members can request a new site. In Step 1 they use a custom registration form to describe the site. A payment for zero$ will be processed as a simple method of assuring they're over 18. Other mechanisms will be considered. Network Members and site members can be under 18, but we'd like site managers to be adults.

On confirmation these users will be sent an email with a unique link back to the site to begin Step 2. They will land on a New Site page where the site will be created immediately as normal.

The user takes the Owner role for their site. Any person can have a different role in any site, including being an Owner in multiple sites in the network. They should be able to use their personal admin toolbar to navigate across sites.

For the most part the sites are completely unrelated. However via Pro Sites one entity may bulk-purchase a number of associated sites.

Owners are end-user content managers, not website admins, not IT-savvy. They get no selection for installable plugins, just tools in wp-admin for managing users, events, forum, blog, chat, ads, maybe theme selection. Plugin-based features will be available at higher pricing tiers.

Network Members generally do not register for instant access to any site. They might apply for manual approval. Usually, Owners Invite existing network Members (or even non-network people who need to create network accounts). The Owner assigns each of their site members a role with typical capabilities: L1=read, L2=write, L3=manage posts, L4=user maint, etc.

Site content is also accessible to specific roles. Site management determines their own rules and caps for specific types.

I will need to remove default WP roles and add new ones. I'll also add capabilities for each role. Some site members will either need a special role with +/- caps for a given site, or I will need the ability to remove specific caps for specific members in specific sites.

If someone has done this I would value some tips. If there is any documentation or video that describes and environment like this, a reference would be welcome. Specific tips are welcome on which features to use from specific plugins.