Well, if we're dreaming, I'm going for broke:

Stop designing surface streets to easily handle high-speed traffic while expecting a little signpost to keep high speeds from being attained. Encourage lower speeds by designing roads that are narrow, with planters and trees near the roadside and/or in the middle of the road, and buildings close to the road (no parking lots along the road... if anywhere, behind the business, not in front). Make people become more active in the process of driving by removing traffic lights and stop signs wherever possible and instead use systems that encourage more natural interaction, like roundabouts or yield signs. Use as little road paint, especially as instructions, as possible. Remove separated sidewalks... if anything, designate pedestrian areas by using a different material (like brick), but without raising or otherwise separating it from the roadway. Legalize jaywalking.

Car-centric arterials remain in intervals to allow the smooth and fast movement of car traffic across longer distances.

I mean, as long as we're dreaming and all...