This one would be a true test for sure, while PeerTube try to address the bandwidth issue by utilizing bit torrent protocol, it still challenging. One idea I can envision is that when PeerTube see videos that are sufficiently popular, it can decide to reduce server bandwidth for it since users are likely sharing bandwidth with each others and reallocate it for the less watched video.

I think any European country that offer unmetered connectivity is going to find itself becoming the hub for video sites.