Since it would technically be a completely new land, I think instead of a small level range, it could have a wide one.
Zone #1:
- Level 75-100
- Level tiered quests (75, 85, 100 each level being unlocked with level requirement checks and qbits). Mobs for people to level off of around the area level, non-aggressive. Quest related gear, maybe.
Zone #2:
- Level 100-125
- Level tiered quests (105, 115, 125). Significantly harder mobs for the level, but still manageable for soloing, mostly aggressive, but still some non-aggressive. A few pieces of gear from the quests/mobs.
Zone #3:
- Level 125-150
- Level tiered quests (125, 135, 150). Another level of hardness, all aggressive. This area brings thoughts of Orochimaru's experiments, cursed seal people and stuff like that. Some useful gear to be found here, but really hard to get without help from friends.