This is definitely a must have and an indictment that this feature (in addition to missing multiple knowledge bases [see here]) is not even planned!
Our customer - like apparently many others - ordered a brand domain especially so that he doesn’t have to work in two systems. Unfortunately, it only seems to work under extreme circumstances.
For everyone who is looking for a temporary solution:
We tried to implement it for our customer via language-related pipelines:
Each pipeline is set in the respective language and then selected as the recipient of the respective CES.
We are currently testing whether it is practical or too cumbersome to bundle multiple service-pipelines in this way.
Maybe it will help someone!