How could email be improved?

I'd love for more dynamic polling, voting, scheduling templates - you know, where people can fill in availability, or select from a menu - and as folks contribute, the data is available for all to see (as opposed to a bunch of text reply-alls)

What do you mean with dynamic polling/voting? Are you talking about more open forms? Making threads available to the public?

Rather than have different email threads, I see it as a network of conversations and it would be interesting to display it like that. People could have access to specific parts of networks (conversations), e.g. public threads, semi-closed (connections of connections only) or closed (network only).