At last, here is the final design of Sony MH1 modified by myself. Should I call this MH-RC?
The overall tonality of MH1 is mimicking a sound power of a flat loudspeaker in a reference room condition, while compensating the equal-loudness characteristic of our hearing system. Moreover, there are psychoacoustic variables such as the tactile sensation & head-shadow effect missing, and they have to be considered too. All these ultimately reflect Mr.Smailagic's philosophy on electroacoustic engineering and I absolutely respect his decision.
However, it is important to remember that a headphone's natural localization closely resembles that of a diffuse-field, and as mentioned previously, if the localization property does not match up, such correlation attempt just falls apart, not to mention that I don't believe in the missing 6-dB effect & passive equal-loudness compensation altogether.
Of course, all the credit goes to Mr. Sead Smailagic for creating an IEM with such an excellent electroacoustic potential. This modification wouldn't have been possible without his support & leniency.