Set "Base Player Traits" or whatever to "Weapon Pickup: Disabled". Then set "Respawn Traits" (under "advanced spawn traits") to "Weapon Pickup: Enabled". You can then set how long those traits last, aka how long they'll be able to pick up weapons for. Because respawn traits only work when a player respawns, they won't have these traits when they first spawn into a game. Simply have all players spawn into a Killball or a death pit when they first spawn to counteract this. I'll try and delete someone who hasn't been online in a while by tommorow.