My problem is that when you add a listing to the website through the admin panel or by the xml import plugin you need to specify a user name who the listing will belong to. But in some cases, you can't specify the user name.
For example: one of the sources of the listings for my site is a listing database of a local newspaper (I use xml import plugin to import listings from a database to a flynax script). Also some listings are added to my website by a managers/agents, who are intermediaries between listing authors and a website. In both cases very difficult and not rationally to create accounts for each of such listings. As I see much easier to create several special accounts for this purpose. But I have some issues with it:

1) Can I create a special account type for inner using on the website, which will be closed for users to register? I didn't find any settings that would allow me to remove an account type from the select field on registration page.
2) Also, for all accounts belong to this account type how can I hide any account info (block on right side panel) and contact form (on the bottom of the listing page) from the listing page? (contacts of the real author of the listing I can show as a field)

Maybe you can advise me another way to solve my problem?

P.S. Sorry for my English.