So I remember there used to be a party system on server where you can invite other players to your party and it shows their distance and gives them a ring around their feet so you can identify them easier. This would help for PVP training, identifying friend or foe, and locating allies who have low health.
https://www.gmodstore.com/market/view/2394
https://www.gmodstore.com/market/view/2394