Finally I'm on holidays and I've had a chance to dedicate myself to starting this modification. While there has been plenty of ideas, sketches and pen-to-paper I've only just now had the time to learn the UDK and make something. The past 4 days have been learning the editor and scripting and so I've focused on getting the game objects created first before I start creating content and levels. After 8 hours of straight programming I have a custom trigger actor which can be "used" and added to the player's inventory. These objects do not require Kimset to be attached and have a customisable static mesh attached. When these items are used they are added to the player's inventory and carried through level to level.
They don't look like much, but they are the first step to making items in game and this is a large section of the gameplay. The next step is creating a HUD for the inventory to display the objects. More updates soon.