Anyone ever rolled the dice and built a 7-8 Ft. Fence without a permit from the City? Apparently the fence builders will build it as long as you sign a waiver with them. I have a very small section of front-facing fence that I don't want to go stand in line for and then wait months for approval.

Lots of people have. You probably won't have any issues, but it's up to you if you're willing to deal with that.

Do you have a neighborhood association? If so, they could be a problem but otherwise probably not likely the city will bother you.

Maybe design it so that the pickets can be trimmed down if necessary, without completely rebuilding?

Don't underestimate the psychosis of your neighbors. When I lived in "busy bodies with too much time on their hands so let's get in everyone's business" central Austin, someone turned me in for a fence that was too tall. The part facing the street was right on the money, and only the parts that turned into the property / not along the street were too tall, so the inspector just gave me a wink and a nod and let it go.