Separate protocols, integrate servers.

Why bridge Matrix/XMPP/OStatus/E-mail/everything instead of using the decently coded, easy-to-install servers already available, and simply integrating them?

Create a usable web interface with OStatus, and private messaging over XMPP/Bosh, add a separate (but integrated) webmail interface. Voilá, a social network for the future, with backwards compatibility already builtin.