My camera marks HDR images quite clearly: They are a sequence of images, where the first second one and third one are equally many stops removed from the first one, and they're usually within a couple of seconds from one-another, with all other settings the same. That sounds like something that should be easy to stack in the import-process, right? Preferably followed up by a rendering to a 32-bit pr channel image straight afterward that is set as the stack top image.

Unfortunately, I don't know Lua, so I won't write it myself any time soon. But such a trivial plugin should exist after all these iterations. Heck, it should be a core functionality!

As for grouping, possibly even a quick pre-rendering, I'd argue there should be a similar Panorama function.

Can anyone recommend any plugins?

Run the following as root to make disks auto-mount during system startup. I use this to have an external disk to put my Tomcat, JBoss and MySQL logfiles on
defaults write /Library/Preferences/SystemConfiguration/autodiskmount AutomountDisksWithoutUserLogin -bool true