Hi Clotilde,
Well pulling out data from IDM is possible not only via VDS.
You can access IDM views directly using for example SAP JPA and JAVA code.
Storing data in IDM is also possible not only via VDS.
You can use either IDM REST API, or you can use again SAP JPA and java code to store data in IDM workspace in a custom table under RT user, than you can setup an external trigger on this table and "on change" event you can trigger IDM tasks.
Best regards,
Ivan