As of now there is only :select (:select video.* or more universal and less readable :execute 'select '.expand('%c:r').'*') and :unselect commands that can help with it. Once selected, usual bulk renaming should help with renaming.
The idea in general seems useful, although needs figuring out more details (should all files be in the same directory or not, what to do with user unselecting files that were selected automatically, and alike).
Is group always defined by a matching base name? E.g. in the example if video.webm was used to select 4 files, changing selection via video.png would imply that webm file is considered part of video.png group and gets unselected completely (otherwise it would cause selection of video.nordlicht.png).