Hey,
I'm totally not to decide here, but just want to repeat my personal subjective opinion on the topic.
From what I do recall from the last PTG, which I was part of, more opinions were inclined towards having some default driver. Otherwise, service is not functional on it's own and must rely heavily on individual organisations to keep support for their drivers without any way of influencing them. In turn, organisations are able to dictate how project should be developed, what changes they are able or not able to do.
I'd say, this suggestion is similar to drop native driver from Octavia or Cinder and just assume that individual organisations will keep support of their drivers.
With that, these service doing just fine with having some default drivers, and some third-party. Also adding third party CI to the service is not huge issue, to ensure that your driver integrates nicely.
With that said, OpenStack-Ansible right now is merging support and CI testing of Vexxhost driver. I also personally highly likely will be using it in future magnum deployments.
But I truly believe, that service without any driver is doomed to failure sooner then later.
If we look at literally anything - automation tool, programming language, service - they all have some core libraries, and can be used, in a way, "out of the box". And here suggestion is to make service and all it's users to put faith in an organisation providing support for the driver, which may be quite tough sell for some highly regulated environments.
In case Magnum is going the road of not having any "out-of-the-box" implementation, i actually wonder if it should stay under OpenStack namespace rather then X, for instance, since it's not self-contained and heavily depends on third party, which might be licensed in a completely different way, as well as change their licensing with time which also put users at tough spot.
But dunno, as I said, this is my very subjective view, and I really can be wrong in this. Also not trying to push any party to any conclusion. So treat it as - one operator voice out of many.