As for structure, the thing I think:

1. Hot Uranus
2. Asteroid Field that extends from outside the Hot Uranus' orbit to far enough away from Pacifica's orbit. There could perhaps be 1 or 2 dwarf planets hidden in the field.
3. Pacifica, moons Minima and Maxima
4. small rocky planet
5. another rocky planet
6. another asteroid field, perhaps with a few dwarf planets
7. Gas giant 1, many moons
8. Gas giant 2, many moons
9. asteroid field #3
10. Rocky planet
11. Ice giant
12. ice field, with many comets, etc.
11.