It definitely sounds simple, until you undertake it. Believe me. I love maintaining my private forums - I have about 15 stickies across 3 private forums that I maintain regularly. It's nice and simple - edit OP, click the box, delete posts.
Maintaining a list? Not so simple. Like I said, take it from firsthand experience: for the first while it's easy as taking a shit in the park at night after splitting a 60oz with 2 midgets. After that it gets redundant and you lose the desire you originally had. Getting guidelines in place is the biggest speedbump... what you may consider a wetlist-worthy offense, others may consider nothing more than a daily pass-it-by occurrence.
I'm sorry for being so blunt and rude, but thus far this thread is another "I want this, but I want you to do the work!" like we've seen so many times on other issues across the board. Don't get me wrong, it would be a useful list - finding someone willing to step up to the plate is the current roadblock and likely that will not change.
Again I don't mean to be a dick to you specifically, you've never done me wrong. But you must be able to see why it hasn't been done yet and why it likely will never be done.