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My vote: #4 - Not a DAMN thing. It all comes down as a matter of opinion (and other things) really:

#2 shouldn't have even BEEN an option. A difference in taste. Not all humans are the same. Don't punish the others just because some others don't like it. Also refer to syaoran-kun's 1st post on page 1.

#1 won't work. Not many people will tag the images properly because of opinions and such...or at all.

#3.....Uh~...that's not really possible because like earlier posts before mine...some people have different opinions about what is Safe or Extreme.....so that won't work either.

So people with weak hearts or whatever: please use Blacklists...OR if that fails for you, go to Safebooru.
Only heard of Safebooru but never went there...so hopefully it doesn't let you people down. Only suggested it because it has "SAFE" in it.....Ha Ha Ha!