- Can Zotero "follow" the attachment, even through name changes and moves (at least within the same drive volume)? Mac aliases behave in this way for example; even if one re-names or moves the original file, the alias will still connect to it properly.

No, we can't do that. The best we could do would be to scan the directory for another file with the exact same file contents. It might make sense to do that — for both stored and linked files — within the same directory, if the file isn't already associated with another item, and show a confirmation prompt after clicking Locate if a file is found rather than showing the filepicker. But for performance reasons it's unlikely we'd do that beyond the immediate directory the file was in.

- Batch commands to seek out the M.I.A. attachments by name, with option to auto-attach if only one exact match is found. Option to limit to a specific search directory as well.

We can't search as efficiently as the OS can, so this is really best left to the OS.

- When using the manual "Locate" command from the "File Not Found" error dialogue in Zotero, have the "Search" field auto-filled with the name of the missing file

We're not able to do that (nor can we control the search scope, and this would only work if it was set to search your whole disk).

Note that, on macOS, you can drag a file from an external Finder window into a file dialog to quickly point the dialog at that file, so if you're already looking at the file in a Finder window.

More importantly, though, this just isn't really a workflow we recommend, which is why we're unlikely to do much here. Most people, even when using linked files, just rely on Zotero or ZotFile to manage the file hierarchy and filenames, with those based automatically on the actual metadata in Zotero. That way Zotero remains the authoritative source of the metadata and things never get out of sync. When the filename is based on the metadata in Zotero to begin with, it doesn't really make sense to rename and move things outside of Zotero and have Zotero jump through hoops trying to figure out where the file went.