I'm not sure why you'd want this... do the monsters actually live THAT long in your games? They sure don't in mine. They're usually extinct by midgame, let alone late. Even the wildland bosses go down pretty fast as it is. So I'm not really sure if it's really worth it to focus into these situations.

Maybe if there were some super monsters spawned through special events halfway or late in games ... that might be something to consider.

I think there should be rather powerfull monsters spawned quite a distance from players starting position, these monsters would pose a semi obstacle, where if you where to take it out you would need a rather powerful stack, giving the map more life. so thumbs up for the original idea.

Sincerely
~ Kongdej