Thanks for initiating a discussion of incident metering. Your discussion is interesting, and added some basic information for those not familiar with incident metering. However, forgive me for staing that in my opinion, significant parts of "the story" have been omitted.
The dial on the incident meter will attempt to make everything middle gray, and hence as you have hinted, a single shadow reading will be rendered as middle gray as will a single highlight reading. To be unaware of the need to double the film speed when metering the shadows ( or raise the film speed as much as you desire to render the shadows other than middle gray ) and to make similar adjustments when metering the highlights, is to invite error.
Incidentally, where exactly should one place the EI? You have chosen to follow the recommendations of the film manufacturer, but correctly infer that each individual must define one's own EI. Many analog photographers have found that the manufacturer's EI values are not optimal when used with the film developer, printing paper, and print developer that one uses. As you might agree, the optimal EI value to use can be defined by testing of one's materials....or through making a large number of exposures as defined below which is, of course, one way of "testing".
The need for testing is mentioned, but hardly emphasized. The exposure of a negative is simply one part of the equation, with film developing adding another very key variable that must be controlled. Certainly "develop for the highlights" has become an accepted paradigm for many analog photographers. One can apply a considerable degree of artistic control by metering the highlights so as to raise or lower the subject brightness range ( as you know, the SBR will help define the developing time by allowing one to deduce the correct time to develop one's film ) and in so doing, control the length of development and the density ( highlights of course in the print ) in the negative. However, how much should one develop a scene for so called "normal" development? If one is indeed using fixed graded paper then the need to be precise in both exposure and development is paramount. Yes, one of the more alluring features of VC paper is the ability that one has to "overcome" a wide variety of exposure and development errors. However, as you state, even those who use VC paper ( and VC paper does have some problems, but such is grist for another mill ) should aim to produce negatives of optimal quality.
So, how does one go about defining one's material? One can attempt to implement the methods of Adams, Minor White, and others in order to define the characteristics of their printing paper and to relate such to the film and developer combination that they use. Such testing methods are most often used by those who use the zone system and reflected metering. One can attempt to learn to develop by inspection as has been done for years, and which method is very well explained by Michael Smith. Incident or reflected metering can be used if one desires to DBI. Incident metering is part and parcel of the Beyond the Zone System approach as formulated and popularized by the late Phil Davis and now carried out through Fred Newman at the View Camera Store. In my opinion, those who are seriously interested in using incident metering would be well advised to read some basic material concerning the BTZS approach. One can of course, go into the field and take lots of negatives in various lighting situations at various EI values, develop for various times, and print the negatives at various filter settings on the enlarger. I would posit that such testing is immensely tedious and can be wasteful of time and materials. Bruce Barnbaum supplies his paradigm for testing in his estimable text...one might go on and on, but the need for testing should not be ignored.
Yes, by all means consider incident metering....however, such metering needs a framework with which to apply the readings obtained. Without an understanding of exactly how incident metering and EI are related to one's film, film developer, printing paper, and printing developer such metering will be subject to educated guesses.