"I do believe some kind of flagging's system would not be a bad idea."
Personally, I do not see a serious reason to change anything but if the administrator agrees that there is a need then we should keep it as simple as possible.
To that end I offer this suggestion:
Slang is where we are most likely to encounter foul language since most of it is slang anyway. Instead of trying to flag individual posts, which might be difficult because it would require immediate action by a moderator and thus, could be viewed before a moderator notices it, maybe we should control them by restricting them to the slang forums. We could tag only these two forums with a warning and move any stray post to them.