This is NOT needed: When searching for an Expedition, friends' and guildies' islands won't be included in the search result any more.
Leave it, as it is - or do the right thing: Use our nicks, so the "PvP" is not against an "attacker". Would make the "PvP" a little more PvP-like.
Most players counter move will be to delete all their friends, and then spending a little more time when on a loot spot.