You say they are obvious but it seems to me that the source port and destination port of UDP are going to be fixed for QUIC, so I'm not too sure those are neces

You say they are obvious but it seems to me that the source port and destination port of UDP are going to be fixed for QUIC, so I'm not too sure those are necessary. Especially since QUIC has connection IDs instead. I don't know QUIC on a deep enough level to figure out if the length and checksum are still needed. I mean I get why you'd tunnel it through a UDP connection, since replacing every single router on the planet no longer seems feasible, but if you want to call it a transport level protocol that's kind of what you'd have to do.