Problem: Admins have the ability to mass-delete contributions of a user seen as problematic. This usually affects a large number of pages; currently it reads 'mass-deleting contribs of user Foo'. Having a templated reason that gets replaced, or a drop-down of common reasons would help.
Proposed solution: Either add a drop-down (with most common reasons, similar to QD), or provide a way that templated reasons get replaced.
Who would benefit: Admins: mass-deleting pages, users: knowing more precisely why the page was deleted