Regarding the spawn system. It seems to me that the vanilla system, when enemies spawn almost everywhere on the surface, overpopulates the world ? In films such as the first The Hobbit, encountering orcs is an event. Maybe it is better to reduce the number of hostile mobs per region, so that they spawn in small groups (30 units) at a distance of at least 500 blocks from each other. Then the invasion will indeed be a big event. Moreover, may be it is better to make free spawn only for military mobs, while other mobs spawn only behind their structures?
It's just that when you walk through the lands of the Rangers of the North, and everywhere someone is fighting with someone, it does not look like an ordinary forests and fields, but like a large battlefield.
If these small groups of enemies also moved in any, but one, direction, it would be even better.
If there are plans for adding new blocks and structures to the mod, may be it would be good to add statues or something like this to show more atmosphere of Middle-Earth. Like Elven warriors or ruined gondorian kings. For example: