Here was the governing principle: sorting out as average people, each Survivor had to become a hero along the game and face growing zombie odds.
So was designed, for each Survivor, a first Skills list acquired along the zombicide. Game effects reflected the different "career" we considered for each archetype... and we wanted to give you the final word!
Successive tests revealed the choice was not only driven by player's taste ("what if I made a sniper of him, or a pack leader?") but by circumstances ("considering option, the best bet is an additional Combat Action...") and Mission objectives (finding food in reduced times is sometimes better). Tests allowed to perfect the Skill trees, until each of us was satisfied to play any Survivor, with any Skill combination. We happened to play the same mission four times in a row without growing weary nor having a déjà-vu feeling. The choices given by the Skill trees extend Zombicide's lifetime!
Beside the progress choices offered to him, each Survivor has his own personality. This is a fundamental criteria for immersion. Of course, this personality is defined by the cool artworks but also from each Survivor's starting Skill. Ned gets a free Search Action because he's madly looking for his bunker lost key! He's feeling trapped outside and gets crazy about it.
The starting Skill defines the role of the Survivor in the group and, from this point on, introduces real interaction between players.

Here's the list!
Amy: +1 free Move Action
Doug: Matching set!
Josh: Slippery
Ned: +1 free Search Action
Phil: Starts with a pistol
Wanda: 2 Zones per Move Action