The third level of analysis that we apply to Naihanchi Kata (Bunkai Sandan) in our dojo concerns what we term 'breaking the mould' and takes the fundamental combative lessons given by the form a stage further. It allows us to explore specific aspects, once the core application framework has been understood.
Vol. 2 of my book series soon to be published primarily focuses on Bunkai Nidan (functional combative application). Towards the end though it also provides a section on Bunkai Sandan and a specific example of this development process using the aspect of limb control, which is in itself a very useful component for self-defence. We have six two-person drills that come from Bunkai Sandan, which may be practised in isolation, or together in flow and then expanded to branch to other kata applications etc.
When exploring the old-school karate concept of Meotode (husband and wife hands), the application of hikite (retracting hand) as seen in many fundamental kata techniques most commonly springs to mind. However, hikite is only one component of meotode, which is itself, a more holistic notion that considers both hands being used together in harmony towards a common goal. This integrated use of the hands, or indeed the whole body, is a vital principle of karate and especially so when used within the context of self-protection.
Developing mechanical habits that see arms and legs being divorced from one another is not only in-efficient, but also completely nonsensical with respect to how the human body is actually designed to operate as an integrated whole. Thus, I would suggest that as a core principle, every classical kata should have the idea of meotode woven within its transitional movements and we should never see body parts moving in complete isolation.