In my opinion, we need to have a way to decide between two cases:

1) traditional autoyast install, user observable behavior should change as less as possible
2) new semi-automatic install that uses autoyast functionality

This could be done e.g. by extending the Mode variable with a new mode for "semi-auto" and then 
protecting some changes by querying for this semi-auto mode. This way we could restrict changed
behavior to cases where new functionality is used.