Why are you talking about hosting a free server for the plugin to use and how much kbps/connections it will need? That will be very difficult to work in my opinion. Just takes 1 bad app to flood and bring the whole thing down. Plugging all the possible leaks and building in restrictions would take the same amount of time as actually building the object.
Couldn't agree more. People can find their own place to host the server, its the plugin that we need! And anyway, you can test your game locally until its released (or in beta) - and if any game actually gets that far, that will be quite an achievement worthy of paying for a small VPS.
Please just GIEF ONLIEN PLUGINZ.
PS. And "nah" to all this p2p stuff. You always need a master server somehow anyway, any p2p apps can still be made if the plugin is well made. (Its basically connecting to a master server, then one of the guys starts hosting the server for the game - im sure you all know this anyway). Theres no need to make the plugin exclusively p2p.