I'd like to suggest a symbology option that allows the user to change the alignment of a vector polygon line stroke to the center, inside, or outside of a path. This functionality is available in Adobe Illustrator, for instance:
This would allow for a more nuanced representation of polygons, including national parks, administrative units, water bodies, etc. There are ways to fake this in ArcGIS Pro and ArcGIS Online (stroke offset, donut effect), but they result in visual inconsistencies, don't scale well, and won't work in vector tiles. Ideally this function would have complete and smooth coverage of the polygon path - either centered, inside, or outside; would scale; and would work in vector tiles.