Whether the person updating a tower/item has not specifically said what they've changed, or they have, but you can't be sure that they haven't accidentally broken something else or forgotten to mention some other change, it would be really useful to be able to see their exact changes.
Suggested implementation: Simply some small window outlining the differences between the respective XML files would be sufficient. Ideally it would display the previous revision and suggested-update revision side-by-side, with the classic green/red highlighting showing the bits that have been added/removed.
I think either make it an admin-only button that'll sit amongst the other admin-only buttons, or auto-attach this an expandable 'diff window' to the end of update posts for everyone to see.
I'm sure you know what I'm talking about, but here's a small example anyway: http://sourceforge.net/projects/tkdiff/
Something like this would massively improve the time it takes to approve updated content, because the admins would know for sure exactly what was changed.