Simple idea: ArcGIS Server: allowing tile resampling.
Change default behavior to resampling: "true" for tiled services. This setting is not explosed as discoverable. It is somewhat related to Resample and Stretch All Image Services
It would significantly enhance end user experience with viewers and imagery.
This would be a "safe" default. Currently, this setting is not exposed. At least in 10.2.2. Correct me if it has been exposed in 10.6 or earlier. A lot of the REST API is non-discoverable and it would be good to continue exposing select settings like this. (or just commonly requested ones such as this particular setting)