BuddyPress.org

Actually that makes more sense than your first post, making multiple services and linking those together is a brilliant idea, I thought you were gonna cramp all of it in one install.

This reminds me of the tuts plus network, what they did is take multiple wordpress intalls and gave every tutorial category their own subdomain ( eg net.tutsplus.com, psd.tutsplus.com etc.). And that network is even part of a bigger network (envato).

Wether it’s possible, I’d say yes, it’s possible. Since your planning on using different servers for all of it.