I guess you could just not really show drops except to each person, and if they picked it up just "magic" the item into the player's inventory. But that requires various packet types that I'm reasonably sure don't work on anything other than Blue Burst.
I discussed it with Soda when he implemented it, and this is exactly how it works. I didn't mention it here, because it's totally impossible to handle drops this way on anything other than BB. The leader of a BB team seems to have a new packet that allows him to suggest drop coordinates for an item without trying to generate one, which as we know isn't the case on Ver.2. Soda's BB implementation asks the leader for the coordinates where an item should drop, and then the server sends a different drop to each client, so each client sees totally different items on the floor, thus preventing anyone else from taking the items on your screen. Drop rates are adjusted to prevent inflated rates from getting four chances to find each monster's rare drop.
When you pick an item up, you simply seek permission from the server to do so, and it works, which is also not the case on Ver.2, since you can't pick up an item without the leader's permission, and unless every client is aware that the item exists, every other client gets totally confused as to what's on the floor and what's in your inventory (which disables your ability to chat and eventually causes you to disconnect, as we've seen in the past).
The only kind of reserved drop system that would work on Ver.2 is a calling system where if you called a specific item at the start of the run and that item dropped, everybody would be able to see that item on the ground, but only you would be able to pick it up. Such a system still requires full inventory tracking, though, which is not implemented yet. If you want PSO2-style drops, you have to play BB or PSO2, period.