@quietflyer Thanks for making me see the light! A victim of tunnel vision, I failed to consider the dynamics in all but the lateral direction. Answer revised. I've also clarified that I'm not intending to present my thoughts as fact. Perhaps chat would be a more appropriate forum? I engaged with this question not because I believe I have all the answers but because the existing material on this topic leaves a lot to be desired and I believe that as a community we can do and should strive for better.

@RobertDiGiovanni Thanks, I think they're a step in the right direction. I purposefully kept the angle of bank constant as per the original question. I'm actually a rotary wing guy so I've tried to keep it as generic as possible - not exactly sure at what stage ignoring the differences between fixed and rotary wing will get us into trouble.

@quietflyer Thanks for the feedback, better than the current FAA diagrams isn't really much of an accomplishment! I have updated my answer to address most of the points you raised. Whilst it is important, we can discuss the semantics of labels later, getting the fundamental concepts right is my focus right now. Hopefully it is now evident why a skid requires more power than a slip - you're turning more! I've addressed the additional drag associated with uncoordinated flight and introduced the concept of efficiency too to make this clearer. Let me know if I missed anything.