I think that's a great idea, I loved hunting mobs in FFXII. But do you mean "instanced" or "public" preys? Would you have to be the fastest player to get there or would everyone receive one NM? Because if you have to compete it can probably lead to trouble somehow.
However, if it's one NM per player then I think it'd be a wonderful thing if SE can keep adding new fights that are challenging every now and then.