The list seems pretty good at first glance. I don't actually have too many criticisms with the initial list. I am a bit shocked at some of the things in A+ rank being only A+ rank. But there really isn't that much disparity between most of the things I think should be ranked a bit higher or lower in that range or in general.SV OU Viability Rankings are now up: https://www.smogon.com/forums/threads/sv-ou-viability-ranking-thread.3712493/#post-9432321
I don't know about Killowattrell being OU and Jolteon, which has better stats and mostly similar strengths, not being on the list. Jolteon is probably the better fast Volt Switcher in most situations besides rain. Personally, I think both are UU.
Is there anything missing? All I can think of at the moment are a couple theoretical mons I haven't tested enough myself. Noivern is maybe good on paper and I've been meaning to get to that. Frosmoth I tested a little. It's only viable if you really devote your Tera slot to it, which might be a non-starter, but it is a decent answer to a lot of special attackers if you do. I can't recall seeing either on the ladder on any of my accounts so I can only assume the usage is very low. Haven't bothered to check.
This ranking is a pretty good start I'd say.