While I do agree that it would be nice if it were easier/possible to play through a firewall, our experience with testing it on the beta team showed that speed was very much an issue.
With several players (I think we had as many as five in one game), if any players are on dialups it can take a long time to get the files to eveyone. Especially if the host is on a dialup modem
This is an area I have very little expertise in, but if changing it to make it more accesable through firewalls is going to slow it down even more, ugh.
Geoschmo