One of my computers used the repos packman, KDE framework and KDE application.
During the upgrade the screen specifying the software gave the message manual
intervention required. There I had probably at least 1000 cases where I had to
choose either vendor change from any of the above mentioned repos back to the
openSUSE repo or break the dependencies. To make the install easier and more
usable (less tedious ticking 1000 times allow vendor change) I suggest that the
manual intervention has the option allow vendor change for all those packages. 

Secondly I think that most users have the packman repos for multimedia where
you have to select for approx 30 packages to allow vendor change. Then after
the upgrade you have to reverse this action and allow vendor change back to
packman. So I suggest that the packman repository can be added during the
upgrade at the time when the 4 main repos are added. 

THis was discussed in the openSUSE forum at
https://forums.opensuse.org/showthread.php/536179-Update-Leap15-to-15-1-what-should-be-changed-in-future