This is a terrible idea. The last thing we need is more instanced forms of gameplay. I enjoy the competitive nature of hunts. Rank Bs spawn every half hour, A every 4 hours or so, and S somewhere around 1-3 days. There's plenty of room to join in the competition, especially if you pick the right time of day.
Please consider that different people like different content. You already have treasure maps and leves; let us have this content the way it is.