Seem to have a crush on this Sony 200-600mm zoom lens

[vision63]

If you get a Sony body, then the choice is made. On the Nikon platform, I'd stick with the Tamron G2 action since it's easy to update the firmware and adjust it. The Sony lens would get the nod for the reasons you mention out of all three of them.

A Nikon NIKKOR Z 200-600mm Zoom Lens is on the roadmap. When it drops, it'll kick all of their butts. However, it'll cost a fortune.