Ghost Recon Wildlands (2017) supported unbounded online co-op, free roam or mission joined, across the ENTIRE 24km x 24km open world. 343i can do better. : r/halo
Ghost Recon Wildlands on Xbox One, PS4 & PC | Ubisoft (US)
Ghost Recon: Wildlands - the pros and cons of multiplayer co-op | VG247
Ghost Recon Wildlands co-op preview: Four-player Far Cry
How To Play Multiplayer - Co-Op & PvP Guide - GameWith