Touché. It has to be short, and start with a strong but pleasant sound. Also, I'd say that the following vowel shouldn't be too tense, I don't think Jim works, either.
And I could add that at least Renegade Shepard doesn't suffer frlom any lack of personality
I'd be of the opinion that Jim could work, though definitively not as much as John, James, or Jack... obviously. Jim is too diminutive.
And I disagree with MC having a "Strong personality", most of what he feels are easily expected reactions, and his definitive lack of flaws make him a rather weak character in my opinion. As for Renegade Shep, s/he reminds me too much of the cliche'd 90s Anti-hero for me to say that s/he has a tangible, unique personality.
But oh well, maybe that's just me being overly negative and harsh.