Vivaldi should support HTTP/2 without encryption.
I saw lot of browsers only supporting http/2 with tls or ssl which is wrong. Lots of small websites like bakery, and small shops does not need https in their website, I design small websites and why not take the advantage of more speed without forcing everyone to use https. An option would be good in Vivaldi to support http/2 without encryption since Vivaldi is made for power users.
Yes, a nice-to-have.
But currently not implemented in Chromium code i guess.
I don't know if it is easy to port to Vivaldi.
SPDY is not usable for you?