RichardG: Would it just be fine if you moved the cape files to a different text document, and then added a config option to disable that checking? Don't know about the Tekkit stuff though.
The real issue is more around the 'Tekkit stuff'. They don't really care about the cape. That can be hardcoded easily. They just don't want IC2 to have an annoying DRM. I do agree that the cape check and the DRM protocol needs to be seperated (for different reasons than what has been stated), yet I don't see how a simple 'cape check' keeps you from playing Minecraft...