This whole situation should have been a "no-brainer".
It wouldn't exactly be rocket-science to change the database query that displays the gallery pages to take into account whether the client browser has the "no nudity" flag enabled and then construct the page html based on a query result that doesn't include thumbnails from images that have the nudity/violence flag enabled.
There would be then no need to have separate rules/guidelines for the creation of thumbnails, people who wanted to see nudity could whilst those who didn't wouldn't.

The only flaw in this scenario would be that some nude/violent thumbnails could get through the filters if their parent image wasn't tagged correctly in the first place, and since this would already be a breach of the TOS the normal mod/admin procedures would apply.

Sorry, there is yet another flaw in this scenario..... it would involve RR in having to pay a php coder to actually do the work rather than getting the users to do it for them without having to change the code-base.