How to create a website generator & Search in everything ?

Hello,
I already noticed the power of Open Atrium and since the new theme, it is even more better. Thank you for this :-)

I plan to create a website and I think Open Atrium is the solution, but I do not know how to create it...

I want to create Blueprints for differents Space types:
( WebRadio, WebTV, Projects, Professionals, ... )
Each Spaces has Content types.
( Presentation, Videos, Events, Audios, Articles,... )
A member is able to create his website based on one of these blueprints an must have the ability to add content in it.
Each space must be located on a subdomain.
( ex : radio1.website.com )
And the content has to be beneath.
( ex : radio1.website.com/programs )

On top of that, I need "Website.com" to be a search engine of content types, to be able to search for videos, articles, events, jobs, ...

So that is my problem, but I can't understand how to create these spaces with the ability for the user to create his own website, based on the blueprint.
I don't understand the Menu system used in OA to create my 'top level' search engine.

And my last question... Will OA survive if I have 5000 or more Spaces ?

Thank you in advance for your help.
And thank you Phase2 for OA.
Have a nice day ;-)
Serge