Ridiculous, yet wonderful idea

There are separate issues.

D2 currently calculates how much loot drops in solo and multiplayer games. These calculation would not change. Therefore, if there is a bias in the number of drops in a single player game versus a multiplayer game per each player, then that bias remains.

In multiplayer D2 games, each player decreases the no drop chance, resulting in more total drops but monster hp increases (normalized to “1 unit of hp” at baseline). The following shows single vs multiplayer games assuming that each player is contributing 1X damage and no one is being carried/can easily overwhelm the content.

So you will notice for coop parties, the sweet spot for loot acquisition rate is 2-3 person parties. Once a player can carry everyone in the party, then the math looks different.