Whats wrong with 24/7 PvP?
Look once the Attacker reaches your PvP Island, it would go into lockdown. Your Buildings would still produce (providing the attackers don't raze you first)
After the Attacker leaves, your Island would stay in Lockdown until you come online. (which means you can only be attacked once a night)
Ill add more features and explain what i just said here more, my new PvP topic should be ready by the end of today.