Well, you can now
Originally I neglected to backup the avatars directory; something I'd completely overlooked. When I asked my hosting provider to restore this directory from a backup that was a few days old, they accidentally restored the whole site, eliminating forum upgrade I'd just done. This was the cause of the second downtime. Anyway, at least it brought the precious avatars back, and gave me the chance to do a cleaner forum reinstall. I encourage you to keep a local copy of your avatar if it is important to you.
Current upgrade status: I've restored all the previous styles/themes except phpVB2. Since template caching directories are no longer placed in each template directory, it's no longer tedious to install / update themes. The current ones date back years; if anyone has any suggestions for newer themes just let me know and I'll consider it (EDIT: forget about it, too many potential issues with mods that alter the templates
). A few mods have also been reinstalled with several more to go. Some of you might find
this page interesting/useful.
Let me know if you notice any problems (except for intermittent stuff caused by my fiddling).