So, the thread still getting bumped three years after I started it really says something about how bleak the market is! Figure I should give a quick update, since I caved last spring and chose what I determined to be my least bad option for 4K/modern video.
This is going to sound comically dumb to mirrorless gurus, but I ended up with:
What's really dumb about this: the lens is for APS-C (aka 1.5x crop) and does not take advantage of the full-frame sensor. So why did I end up with the A7r ii? Well, it was about the same price as newer Sony crop bodies that shared the A7r's in-body stabilization, which I really wanted for video. (To be clear, the A7r series features "Super 35" mode for video, where only the APS-C subset of the sensor is used).
This setup ran me about the same as the mid-range Sony 4K camcorders, but it gives me substantially better low light performance... at the expense of ergonomics and size. I was attracted to the 18-105 because of its wide focal range and its power zoom feature, which at least allows me to zoom smoothly during video like a camcorder if needed.
Using it last spring was a learning experience, and I totally flubbed focus for portions of every tornado I saw. Still, I think I'm reasonably happy with it... I just need to practice focusing more before next season arrives. A couple samples shot with this setup:
Vernon storm:
Sudan/Earth storm:
In theory, I could get a Nikon F adaptor and use the lens lineup I'm already using for stills on the A7r ii, but I haven't messed with that yet. Honestly, I'm now stuck with the same paralysis about where to go next with my gear for stills as I was with video a couple years ago... but that's for another thread.