Hi Martin and others,
I experimented a bit further with this, albeit rather unsuccessfully from the view of useful results.
While the "target system" field is intended for navigation to the corresponding trusted RFC connection, it is also possible to turn the user menus off. So such a remote role is not going to go anywhere in navigation. If additionally the CUA is active and you create all the target system single roles in the CUA master system as well and assign them to the "target" they are intended for... then the single role menu is transferred to the child system which the role has as a target. But only the menu, and leaves the role in the target as status red. That also means it is only useful for component neutral roles.
Now comes the hack: If you create a composite role in the master system with local single roles as well but the single roles are assigned to "targets destinations", then when assigning the user to the composite role in the master system, then it also assigns the single roles in the target systems to the user as well as the local system (the master as a child of itself). So it is in fact a halfway business role in the IDM sense, with some naming convention strings attached.
You also dont see this in the code of SU01, as the USERCLONE Idoc processing seems to be the guilty one to also send aditional Idocs for these single roles with targets assigned to the roles and not the user.
There is only one major show-stopper in the design of the thing: You can only assign 1 target RFC connection to a single role in the central CUA master system but have to maintain the roles in the target logical system still. That means that roles must be maintained logical system specifically. That also means that you have to maintain the roles directly in production and have a completely different set for development and never transport any roles. They are as unique as their CUA master system "target destination" value and that is the logical system name as well.
That is a bit of a bummer because it means that you also cannot ever test anything...
Did anyone ever try to actually use this?
Cheers,
Julius