B2B Restricted Access to Catalog and/or micro site.

Hello CS Cart Community - I am seeking advice on how to approach a problem - likely a custom development, but I would like help understanding which capabilities I should focus on and whether such a modification would be feasible.

CS Cart Multi-Vendor Ultimate 4.16.2

Marketplace is B2C and B2B

Option 1 - B2B Vendors should only be visible to Vendor Plan members in a certain tier (let’s say gold).
Option 2 - Customers of the B2B vendor should be added to a user group before being granted to the micro-store and catalog items.

Why? The default market-place is open to the public. B2B sellers do not want to expose their catalogs to the public. B2B sellers only want to deal with other businesses (gold plan is only available to registered businesses).

Optimal solution - Customer must apply to B2B Vendor for access to the catalog. Vendor can approve. In other words, this is a whitelist model. In theory, this should work with user groups?

Ideally - if a customer browses to the B2B vendor micro-site, if they are in the right customer group they should see the vendors catalog. If they are not in the right customer group then the site should display a custom HTML block. The custom HTML block would say something to the effect of…

<Vendor Micro-Site - Not in the Customer Group>
Click here to apply for access to this vendor
Click here for a list of sellers on this platform that carry our products

I understand that some of this will be custom development, but I am hoping that some kind contributor can help me to understand the existing capabilities and frameworks so that I can properly articulate my requirements to a development partner. This will also help me to understand the scope of development work that I can anticipate.

Side bar rant… How is this not a feature already? In a B2C & B2B marketplace, it must be possible to restrict the customers in the default B2C group to not see the B2B content? I hope that I just need to learn more and then I will understand that this is possible. It cannot work that wholesale catalogs are exposed to unregistered and registered users? What am I missing.

This means a lot to me. Thank you.