You can set the origin for new names/text in the Settings - Schematic Editor - Text and applying lower center as the default will help for horizontal buses, but it does not help with naming vertical segments and we don't currently have separated settings for this. If you consider this a useful enhancement then you should post it over on the Mentor Ideas site: POST data
The only other solution as you infer is to write some automation to do this post placement.
Thank you for your reply Robert!
Changing the default origin to 'middle left' is not sufficient in my case since this will cause the label to be positioned _lower_ than if I choose 'lower left', meaning I still would need to move the label one gridpoint up or otherwise the label will be overlapping the bus more or less completely.
However, I reduced the problem somewhat by changing the default bus line width from 10 to 7. This will do as a workaround for the time being. Perhaps I will write som automation to solve the issue in the future if I can find the time.