Overall a great game! Taking out the day timer gives a good sense of flow to things, and the ability to enter lockers and accelerate the collection always gives players something to do. It also helps with crowd management.
The pocket dimension is nice, although it'd be better if it could be worked into the story and hallway gameplay. How about when you enter a locker, you can choose to keep a girl instead of releasing her. That would trigger an animation that would drag her back to your realm. Your selections could just be displayed on a list, but a cooler option would be to have a wall of capture pods that hold your harem. My first thought was clear 'stasis' pods, but it could be a meatwall or some other containment device as well.
From there, my ideas would probably turn it into an entirely different game. A way to interact with your harem directly, romance them, and recruit them to your cause. The reward would be them pushing girls into broom closets and elevators for you, causing distractions, and opening access to other areas of the school.
On the bad side, the upgrade grid needs to be cleaned up. Not really a fan of the random bingo card where I may be moving in the opposite direction of a new pod type, and unlocking upgrades.There should be some kind of structure or path.