I am going to watch that interview in a few moments.
A couple of thoughts. First, I admire you for the undertaking, which should be useful in a broad sense. The more we understand about what kinds of distortion matter, the better. My sense, though, is that this may be something that is already understood fairly well, thanks to prior work by a variety of other researchers. As such, before undertaking something as ambitious as what you are undertaking, I would first search the literature exhaustively. In fact, a paper that definitely summarizes the existing investigations and findings would be very useful all on its own, possibly deserving of publication, independently of the independent research you are planning to do.
Almost all the studies I have found concern the audibility threshold of various forms of linear and non-linear distortions, not if these can be used to improve the enjoyment of listening to real music. I realize that it is much more difficult to quantify this in numbers, but in the end this is what matters most to an audiophile and has probably not been studied in detail. If you can find something about it, I would be happy if you share it, maybe it will save us some work.
Second, I cannot help but notice something that seems a bit curious, in what you wrote and that I excerpted above. You alluded to realism, i.e., "the illusion of being in front of the live musical event". Implicitly you are saying that in order to achieve this illusion, the sound must be altered so that it does not sound the same as what was recorded the live event, in order that the listener's emotional response will be more like what it is for a listener at the live event. This is what you are saying in essence, and since it is, it seems to me that you should state this in the plainest manner possible.
On the second point, perhaps I have not explained myself well. In an ideal world, where the whole chain of production and reproduction is perfectly linear, I don't think it is necessary to deliberately inject any form of distortion to achieve a sense of realism in reproduction. If it is added in production, it is for artistic purposes. In the real world, unfortunately, electronic devices in the whole chain introduce "bad" unwanted distortions that can destroy this sense of realism of the original source (one of the aspects of listening pleasure) that an audiophile is looking for. By controlling the injection of "good" distortion into reproduction, it should be possible to recover some, if not all, of these qualities using the extensively studied ear masking effect. Obviously, assuming the source material is not too compromised and the sound engineer has done his job correctly (e.g. if he introduces digital clipping, one of the worst distortions, I don't think much can be done).
Third, I don't think that there can be any genuine reason for not giving the listener the ability to control the level of added distortion. I think it self-evident that it is highly desirable for the listener to be provided the ability to control the level of added distortion, and even the ability to vary the makeup of the distortion. It is self-evident to me that the listener should be given control over anything that alters sound in any way, including the ability to disable the effect via a by-pass switch. It follows (directly) that any distortion added to amplification should be thought of as adjunct processing. I do not know of any good, genuine way to avoid this observation, yet this observation is never made by people who advocate that it is desirable for amplifiers to add distortion along with the amplification. This strikes me as patently disingenuous, and this is the stronger of the two reasons why people who argue for distortion in amplifiers seem disingenuous to me.) ...
On this point I agree with you. I would prefer to have reproduction chains that are as linear as possible. Then, eventually, the user can adjust the "good" distortion injection as he prefers on his preamp. What I can add is that it is very complex to independently control the second harmonic and third harmonic distortion in analogue, leaving the other harmonics unchanged and at negligible levels. My designer friends are thinking about it. Anyway, if you have other types of tests in mind by working on the tracks digitally I am open to discussion.