I think P2P has stood the test of time. Torrents scale extremely well, any large scale video would have so many peers the server wouldn't have to participate at all. These days most torrents easily saturate my gigabit connection no problem with just a handful of peers. Torrents tends to spread like wildfire.

The main issue would be storage space, but I think a lot of YouTubers would be perfectly okay with spending $5-10 a month to pay for the storage costs with all the benefits you get from not being tied to YouTube's ToS and policies. It's a drop in the bucket compared to the earnings from sponsor spots.