preface: i am not a tech guy and dont know if it’s possible
Be able to host a server on your pc that doesnt effect progression and doesnt appear in the server browser, you can choose which map and invite friends.
Additionally, there can be a mod menu so you and your mates can muck around more. Mod menu would have options like, freeze timer, respawn all vehicles, restore destroyed buildings, toggle no clip, unlock all weapons and attachments(in the server not outside the server like the range, infinite ammo, time multiplier, gravity slider, etc
Purely a way for you and your friends to fuck around