First, the issue you are describing (the spacing between subjects) is not really a zone system issue; it is a lighting issue, it can be solved with a touch of artificial light on the skin or when printing by using some judicious burning or dodging.
Second, yes, changing contrast rate does shorten the range of what prints from the film allowing the skin to print lighter. That's not always a good choice though. Micro contrast and skin texture may look right at normal development and easily look strained at +2.
Third, there are 11 print zones in the classic zone system, those zones have 11 corresponding zones in the scene, they all exist regardless of how many stops wide the scene is; if you doubt that, I suggest you go to the horses mouth and read "The Negative" by Ansel Adams.
That is not to say that the classic zone system is the only good way to think about visualization. People apply zone system principles in various ways.