'Aight, bottom Line:
- the adaption by the UI of the BADI logic is a little slow sometimes
- the 'ALL' profile entry is completely ignored from the Customizing, it's instead statically controlled by the iView Attribute "Add ALL Substitution Profile as default" which also means, though it can't be controlled dynamically in the BADI
- if you have a lot of different processes, the profile list and the combinations required in customizing grow innumerably and become "bloated" because only one substitution profile can be used for a role at a time (this one will meet resistance on enduserside :-/ )
I'll mark the thread "assumed" answered, because my initial problem is, well, "solved", kind of. In case there are additional problems, I'll open new dedicated threads.
Siddharth Rajora thanks a lot for your replies, they pointed me in the right direction, i.e. made me research the right terms
Cheers, Lukas