There seems to be an inconsistency in the usage and effect of the interaction scheme and the mouse mode: They seem to mix their level of responsibility.
The Interaction scheme can change from MITK scheme to PACS scheme. This is done by setting a property in the editor's preference page.
Using the render window menu of each render window inside the multi widget editor, the user is also able to change the interaction scheme to rotation scheme, swivel scheme etc.
However, these interaction schemes from the render window menu only work with the MITK scheme, so they switch the interaction configuration back to a (modified) MITK interaction.
The PACS scheme can also be modified by using the buttons inside the mouse mode toolbar QmitkMouseModeSwitcher. Here, the different modifications are explicitly called MouseMode, which is inconsistent compared to the MITK scheme.
My suggestions is to have two interaction schemes (MITK and PACS) and provide different mouse mode for both of them. This would also allow us to redefine the .xml-config files and reduce them to a minimum of xml lines.
We should consider this while reworking the mouse mode switcher classes.