Matthias,
depending on your requirement I think this is achievable (maybe I don't understand correctly).
Let's assume you have two systems:
- GRC
- ECC
If you have the plug-in (GRCPINW) installed on both systems and configured decentralized access so that you can use the /GRCPI/GRIA_EAM transaction in both systems. If you assign Emergency Firefighter IDs and authorize them only in GRC (for local firefighting) you can start that either via /GRCPI/GRIA_EAM or GRAC_EAM transaction. Other FF IDs like Support you create and authorize only in the ECC which means it can be used decentralized.
For sure if a user has access to GRC and is assigned to a Support FF and he/she is able to start centralized Firefighting (GRAC_EAM) from GRC system the this can be considered as centralized (but here I don't see an issue since this gives the users more flexibility).
If my assumption or your concern is different please let me know and share an example.
ps. from configuration point of view (parameter 4015) it can only be set YES/NO at once.
Thanks and regards,
Alessandro