There is absolutely no reason for an HAA operator to use (c) anyway  

FAR 135.267(c) is an exception to (b) so that certificate holders can use HIGHER flight time limitations if they maintain regurlarly assigned flight schedules.   It increases the daily flight time limitation from 8 hrs to 10 hours.   There is virtually zero chance any HAA operator will get 8 hours of flight time in a 14 hour day.

Even if it did, it is so rare that an HAA operator would be inefficient and ineffective to try and keep a regurlarly scheduled duty day, as defined as not changing your start and finish times for at least 4 weeks straight.   A typical base has 4 pilots, most work a 7/7 schedule CHANGING from days on one 7 day "hitch" to nights on the next "hitch" of 7.   Or, they operate with a 3day-4night/7off (or 4day-3night/7off), or something similar.   IOWs, they CHANGE their duty times REGURLARLY, which does not qualify for (c) authorizations.

Pilots wooudl be restricted from picking up workovers unless they conform to their regular schedule, which is a rare occurance, particulary if its at another base with different start/end times.

HAA Air Carriers simply do not operate under FAR 135.267(c) in practice!