On of the core principles of Wikipedia is "be bold". Be bold is a very useful principle as it allows users to take actions that are then easily undone when other users disagree.
Unfortunately, tools like MassEditRegex can't be used in that way because it's not possible to simply undo the work of a batch with one click.
On the Wikidata side the problem is even bigger. Given that it's not possible to undo the effect of a merge action on Wikidata with one click given that it works on two items, the merge function gets hidden in a gadget where new users don't immediately find it.
It's also really hard to undo a bulk edit of items via a tool like quickstatements.
If it would be possible to have a type of edits that would affect multiple pages and that can be undone as easily as an edit is currently undone, that would allow us to allow more tools to be used that affect lot of data while still being able to easily moderate their abuse.