I'd be in support of that! Maybe use the "extra" field in kind:1 in combination with a tag in the "tags" field to make these both discoverable and visible to normal clients. Or just use a tag that links to a special-kind note insted where all metadata can be found, so that clients that support it, can show it as an embed.

Meanwhile, just querying a relay for `["REQ", ["kind", 999]]` would return only those "video notes".

I think there's something in this =)