Could we get a clarification?
So only missions and vendors are locked by Street Cred NOT access to portions of Night City? (i.e. the map)
Thinking about it this makes sense.
Street Cred (or at least this is my guess) is how well known you are to the people arranging or hiring for jobs and "exclusive" merchants.
After finishing specific part of the game, you will be able to roam through Night City freely, just like in Witcher 3