We have the same problem, the only way I can see of putting the control of drill paths in the report developers hands (and hence not prompting the user) is by duplicating the objects in the Universe which is the option that you disregarded.
The universe allows this flexibility, plus we also do not have that many hierarchies where I am so I was thinking of creating a report hierarchy class, and then defining sub-classes for each custom hierarchy in which would be the dimensions relating to the drill path. I would then create a custom hierarchy using these drill paths.
Not pretty, increases universe maintenance, but by putting them into separate classes it does make them a bit easier to look after and the report developers know which objects relate to which drill path at design time.
This posts poohpoohs this idea though: https://bobj-board.org/t/142706
I would like to hear what you implemented in the end.
Darth Services 
(BOB member since 2007-11-20)