Night Kiss work in a very laissez-faire manner. They are made of people from diverse backgrounds with unique skills and quirks, so whoever is best suited to lead based on the job will do so. I would recommend thinking up your character's background and how they got into this business then what skills they'd likely honed based on their personal preferences and history. I'd expect most of our team to be somewhat experienced, so, wager they've put in 4 years into this work and likely have something they are very comfortable with. It's alright for these sorts of skills to be redundant, the CS I am drafting will make that work just fine. Pecking line isn't really a thing. New members merely are a mystery, so if you want a younger, new initiate it just means people are less familiar with what you bring. Everyone has a job and was accepted for a reason, the whole just may not know what that was yet. I will probably begin the plot after a significant amount of time away (say, it's been 6 months IC since the team's been gathered) so everyone enters on an even playing field. 

To answer about hierarchy and skills otherwise, I should say this. Missions will highlight happenings in the greater world and require success in a few areas to accomplish. The Night Kiss may be hired to kill an innovator of clockwork and slow advancement, for example, by the tech-fearing village across the way. That means there's at least two things that must be done: 1) Kill the innovator & 2) Steal plans, destroy prototypes, etc. Both objectives probably require very different skill sets, so diversity as a whole is important. Leadership will shift with the most relevant to the job. So our most stealthy or charismatic (good w/ disguises) might lead the second objective while an apothecary, archer, or any other type could lead the first. The group will decide how to go about jobs too, so things should stay fluid. To be clear, my character will be more a facilitator and guardian of the Night Kiss than a top authority.