We have a customer that writes all base content in "en" and uses that as template for all other languages.
When other editors are translating to their local languages they use "compare different versions" and translates from "en".
Is it possible to allways compare to published "en", currently it fallbacks to published version of chosen language.
The list gives all the previously published versions version (including the all the languages) and you can choose whatever language's latest version to compare with.
And, there is no out of the box options availble to configure the 'en' only to compare as default.