There are many Amateur mods for multiplayer sandbox (epoch, exile, various life mods where a huge number of units items and vehicles). You also had a ready-made co-op mode for Apex. Well, again, you can make a compromise so that the tasks are simply duplicated on the partner, or at least the first player was the main one and all interactions were conducted with him, and 2 (3 or 4) player(s) were just "empty dummies" without the ability to interact with the game world (we are talking about the gameplay of the mod, from which you can leave only automatic rapid movements if the main player teleported) while the "vanilla" options should be available (shooting, vehicles, etc.). Thanks for understanding. Please think about it.