Note: You can do it Offline, Open Console and type Switchlevel Obj_DomeRedux press Enter. For Javelin type in the Console; set SGPlayerReplicationInfo m_SlotArcheTypes FieldOps_05_Gameplay.Pawns.A_FieldOps_05
She will be replaced with the first Merc in the Squad (pic doesnt change tho)
For Unlimited Ammo and no Cooldown type in the Console: set SGPlayerSetCooldown m_AbilityCoolDowns (m_autorate=10) | set SGCooldownComponent m_energycost (0) | set SGInventoryManager bInfiniteAmmo true