I think a nice addition to the API would be the ability to create our own upgrade modules. I have been looking through the IC2 code and as far as I can tell, there is no way for me to add my own functional upgrade without modifying the TileEntityElectricMachine, which is usually bad practice. I'm not sure how easy it would be, but perhaps allowing us to access all of the general variables of the ElectricMachines (IE, maxInput, operationLength, maxEnergy, etc) through an API class or interface would work. Just an idea, as my in-progress IC2 addon is adding some upgrades that can be used on my new electric armors, and I think it would be cool if they could be used in the machines as well. I can allow them to be placed in those four slots by extending ItemUpgradeModule, but they won't actually do anything without modifying IC2 classes.