I guess it's not that easy. For german users it is. But take a look at the keyboard layouts yourself and which are available....
There is "English QWERTY" and "Englisch AZERTY". Which one would you think should be used automaticallly if the choosen language is English? And what about a user who want to have it different? What about users from a country where no specific keyboard layout exists...India or Italy for example?
So I guess this won't happen. I'm just thinking of a french user who will live in a different country. So that user might need the french language, the french keyboard layout, but a different timezone....so it gets more and more complicated to fit any user case. For now it's the same for everyone. Everybody has to change the settings. There are some automated ways if you use CEC. As for that Kodi gets its informations to which the TV is set to and select the specific language directly.
BUT...
I agree that the menu shouldn't jump back to the first entry of that settings menu after the language change, so that users could notice there might be other settings to change. For this, as it's the standard skin for Kodi itself (and I would say it's a skin thing), I guess you should report at:
Kodi Community Forum - Estuary
The other thing you mentioned (set the movie scraping) won't happen, I guess...there are still movies on the database Kodi scrapes from which aren't avaible in any given language. So nearly for the same case like explained above (for users from India for example), they have to set the scraper to EN instead of their mother language. Because if the scraper might be set otherwise, it might not find ANY movie, because it simply doesn't exist in the database for that given language.