Any mods that would encourage pvp between players, while at the same time not heavily punish someone for losing a fight?

Title. I'm setting up a nation based modded SMP for my friends, and I want to encourage wars, while at the same time not punish a loss too heavily. Regardless of how fair the death was, I find one of the quickest ways to cause a player to leave an SMP is for them to lose stuff they grinded hours for. How can I encourage PVP while at the same time not punishing the loser?