I agree with Peter - Web Mercator (WKID 3857) is not recommended for making measurements on a printed copy using the graphical scalebar because of its distortions, especially closer to the poles. Measuring distances and areas when your map uses the Mercator projection However, you can request the Esri basemaps in a different projection, if you are working on creating a viewer. You just request them as a dynamic map service (now called a map image layer) and add them as a layer to the map object. They will render slower and you will notice the jpg compression. However, it is possible to add Esri basemaps in your viewer in State Plane in this way, and State Plane if you are in the US is one the better choices in general if you will be making measurements based on the scalebar. Otherwise, choose your projection based on which you need to be most accurate (distance, direction, shape, and/or area). How to choose a projection
Also note, the Print widget in the WebApp Builder actually has an option to set the printout result to any projection. Such as state plane. However, I was unable to get it to work, it appears at the moment to have some sort of bug with reprojecting which I'm waiting to hear back on: https://community.esri.com/ideas/10523#comment-76402
