As I mentioned in the whole debacle over Kepler, I would also back something along these lines - though for the sake of simplicity I'd propose that an attack declaration through "an old enough account with enough posts" should do the trick.
I think RP for these things should need accountability, 'sall.
Quick Edit for Kahl: I think the issue has nothing to do with people declaring attacks, but with attacks being declared when there are noone to truthfully account them for.
