@Astek: Well if you make a cam do all the work.Like If you press WASD it would move, and alsoMouse, and Shoot and everything is prossible (wich is). Then just apply a scaled weapon, and scaled ammo for the player to use, add you scripts, so if near it will add to inventory (also possible in plysmod) and then it would rase the ammo quantity (possible) and it would arm your cam with gun (possible). So basicaly with scripting it is possible to do this.
But if this is a mutlyplayer game, you will have a hard time on getting this into Arena mode, anyway it is possible.
Good luck.
EDIT: You can also make a Skybox.
and then just a part of where the player goes, scale that up. So less things to scale.