I would like to rename a number of files in one operation, but it does not appear that pantheon-files supports this feature.
Pantheon-files does not currently support bulk renaming, however this feature is on the wishlist.
You could do that by integrating into Pantheon Files' context menu an option to use the bulk-rename tool of Thunar file manager, which has many other options than by just one rename-pattern.
sudo apt-get install thunar
gedit as text editor:
[Contractor Entry] Name=Rename file(s) in Thunar Icon=thunar MimeType=application/octet-stream Exec=thunar -B %U Gettext-Domain=pantheon-files