So the trouble with chi seems to be that both chi-lovers and haters present or expect chi as being something special, something extra to the normal range of mundane experience. I would suggest that chi is little more than a category, different in intent and purpose to any other category in our "|Western" experience maybe, but still referring to sensations available to all people. In my opinion, chi is simply a different way of labelling sensations, in such a way that one can use these sensations to concentrate, feel the tides of the body, and gain energy and calmness from this process. The human body is broken down by Western medicine into the respiratory system, the cardiovascular system and so on. But none of these is a discrete "thing". These systems are all interwoven and interlinked, labelled for convenience, and the expediency of medicine. What "qi" introduces which Western medicine tries to avoid, is some idea of faith. The dictates of qi say "do me, cultivate me, try me and then see if I exist or not." Western medicine doesn't care if you believe or not. Of course, we also know that if someone feels that they are going to get better, this seems to help the process. If you follow the dictates of qi, you will create qi, or you will create the results of the qi system of work.
Really, if we had to boil it down, I'd say qi is flow. I've never come across a use or definition of qi where it wasn't recommended that it should flow. So whether one is talking about hormones, blood, breath, artistic spirit, or martial intent, flow is key. Flow implies interconnectedness; it also implies that any work to be done is about clearing the path to let the stream flow, rather than carrying the water to the destination in a bucket. Whatever qi is, it is "already there", which speaks of potential in all places, situations and beings. We don't need to do Taoist alchemy to benefit from flow. It's not mandatory because it doesn't add anything that's not there, merely changes the way one looks at it. That's all for now on this topic.