One thought we've had is that it'd be nice if there were symmetry between attacker and defender in that: If you go on the offense, your production line is left vulnerable. However, this ambition is easily foiled by the creation of specific war villages, or the like, by which the symmetrical risk the attacker takes through attacking is partitioned away to a meaningless alt village without meaningful production lines.
The perhaps best realization we've had of this thought is that of a "Raid Moon". I.e. a server global time window -- eight hours once each week, say -- during which the game takes on more the character of a free for all; raiding is significantly easier. Under such conditions it is by definition true that the state of being able to attack someone is intrinsically linked to the state of being oneself possible to attack in return.
Under a "Raid Moon" system, however, it seems likely that PvP simply becomes a question of who can leverage more combat ready characters. Is this desirable?
Please discuss.