I take it you want to operate 2 separate Dolphin sites with totally different content, but use one of the databases for remote authentication only, on a second site?

I could be wrong, but I don't think you'll get Boonex to even consider this, and you'll most likely have to hire a pretty good coder to do this. You'll need database remote access enabled on both sites, so it would help if they're on the same physical server. Shared hosting is out... no hosting company will enable remote access see more on a shared server.

This can get a little tricky because one of the sites will be working with 2 databases... one for the remote authentication, and a local DB for everything else.

It might be easier to setup some sort of cross-site scripting to periodically update the DB tables in the secondary site with the user authentication info... every hour or so. That might get around the need to enable remote DB access, or changing a lot of code.

It's a neat concept, and I can see a lot of usefulness, but I don't think you'll get Boonex to work on it.