Currently if you wish to create a section you click on a start point and and end point and the view distance is automatically generated by Revit through some algorithm. I propose that the section creation controls are changed to a 3-click system where the third click is used to define the distance of the section. A dashed box can preview the area in the section as you move the mouse after the 2nd click in the same way that the section previews the area currently if you click on any section (a dashed blue line pops up showing the extents).
Additionally, for improved usability, a user should be able to click the start and end of a section, and with the third click point to a point behind the two points to automatically flip the section to the other side.