Better yet, extensions to implement BitTorrent extensions? Such as the mutable torrent BEP and others? It'd be great if this spawned hundreds of top quality BitTorrent clients

Build your own Extension

To limit the scope of the challenge, I had to leave out a lot of cool features you see in modern clients: magnet links, UDP trackers, DHT

I'm planning to add them over time starting with magnet links which is the highest voted extension idea right now