The more I think about it, the more I like it.
Getting a kill in valor form or with skystrike should reset your QWE.
Ult should probably stay as is, because it would be brokenly OP if you could just extend your valor form indefinitely.
But yeah, a lot of times when I see 2-3 mid health enemies nearby... I can engage on one, assassinate them while keeping valor form... but then I'm just flying in circles waiting for my cooldowns because I can't really just fly in and start auto attacking the other targets. That's suicide.
Because of the huge cooldown on your ultimate, you should definitely be able to get in more skills during Valor time.
You are always still at risk of getting hit with CC... which stops any assassin as it should... But at least you aren't just flying around at super speed doing nothing.
Having QWE reset after skystrike kill would be fantastic for at least having a chance to disengage on enemies who are now right on top of you after you killed their teammate. As of now, if you fly in and assassinate someone who is near a teammate, that teammate will 100% be able to stop you afterward. At least give Quinn a chance to get away outside of using a Summoner spell.
Also, it at least makes more sense doing it this way since honestly Quinn and Valor should not be sharing cooldowns in the first place. They aren't the same entity so it makes no sense how Valor using vault somehow means Quinn has to wait to use her own vault. One is a bird and one is a human. Why are they sharing cooldowns? Quinn isn't actually transforming into Valor. Valor takes her place on the battlefield.