Great idea, though the execution is lacking in some respects. Biboo's attack is impossible to dodge and feels very unfair, and I did not realize Shiori could be shot directly, so I had to slowly whittle her down through her summons... Which took almost all the ammo in the entire level. I also couldn't tell if other Advent mascots could be hurt- usually I just elected to shoot the boss and take them down ASAP.
Also, I cleared the final fight against all 5 without depleting Shiori's health bar, which felt like a bug.