Dolphin across multiple sites

We are to create a number of specialized dating sites. It is our aim to setup a system where multiple sites share the same user database.

Each Site must be able to have it's own Template.

The user is able to register on any of the dating sites they select during the registration process or later in their profile. Depending on which sites they have selected the search results must only return users from different sites who have also subscribed to the site this user is on.

For instance:

User1 registers for site1 and site2.
User2 registers for site2 and site3.

When user1 searches on site1 user2 must be returned in the Search Results as they have a shared interest. i.e. site2.

However user2 should not appear in search results on site1 for users who have only selected site1.

With regard to the features, top rated and top members on each site should only show members who registered on their site. i.e. site1 only ever shows users who registered on site1, site2 only ever shows users who registered on site2.

If you have any questions please drop me a message.