Would PvP be ruined if...

[shiznitz]

Have not read the full thread, but the idea you are proposing here is in almost every mmog out there.  It is called /duel.  And it is rarely used.  Your 'attack' here is someone initiating a duel and the other has the option to decline or accept and get in the first blow.  Nothing new really.

In a sense, but /duel doesn't expose the aggressor to the retribution of the target's group and doesn't allow the aggressor's group to join in if the duel is accepted.