Sure, and that is the real battle, who can get an external IP! Yep, I'm ok with the P2P stuff to be over UDP, but if you ever made UDP hole-punching work you w

Sure, and that is the real battle, who can get an external IP! Yep, I'm ok with the P2P stuff to be over UDP, but if you ever made UDP hole-punching work you will realize it's not necessarily the most straight forward solution. P2P does not scale for all problems, while distributed client/server does! The bottleneck never was network bandwidth (binary vs. text), it's been atomic parallelism since multi-core processors peaked in concurrent RAM bandwidth 2014+ after DDR4 increased latency. Copying files is not a problem because you can always make files smaller by reducing quality!