It would assist structure creation a great deal if each of the NPC Faction NPC's could have a spawner block that spawned 1 of each type, in the same way that Better Dungeons spawns its NPC's.

This allows a structure builder to set up a structure in creative and place NPC spawners of the correct type in the right positions so that when the spawned structure is encountered by players in game, all its NPC's do not spawn at once and rush in a mob to attack them.

The spawner block would:

1 Not activate in creative mode

2 Be individually configurable after placement to set activation distance from player

3 Only spawn one of the given NPC type and disappear afterwards