For example they can do a to do list daily. Same reset time as the missions. But for example.
1. Clear 1 > 3 > 5 > all Daily missions.
2. Use 5 > 10 > 20 > 30 Arena points.
3. Spend 10k > 20k > 50k > 100k Money (On stat/pachinko/girls)
4. Complete all 3 for a 5% girl drop chance (Possible limited to the daily task only?)
This is all just quickly taught about, not much orginally compaired to OI or Kanpani girls, or other nutaku games. But it can follow the lead and add a new limited girl to them, as the others don't have that.