SAPUI5 application for manual start of SCPI Extraction process

Hello Community,

I have a question regarding architecture of a custom application and we are not sure how to implement it.

We want to have a UI5 application to trigger a process in SCPI which will do an oData extraction of data, and transform it into a file to be deposited in an FTP.
SCPI process is trigerred by URL with parameters.

We want to deploy the application to S/4HANA Cloud to benefit from the Business roles and catalog but when doing that, we encounter the Cross-Origin policy as the SCPI URL isn't part of S/4HANA Cloud servers.
If we deploy the application in SCP, we won't have the Cross-Origin policy blocking us with the destination service, but then we lost the benefit of the user roles declared in S/4HANA Cloud. I might have missed something but I don't see how I can deploy a UI5 app in SCP without having to do user management in it (duplication of user creation, role gestion, ...).

I hope I explained correctly the problem, but do not hesitate to ask for more details.

Can anyone kindly advise on how to proceed with this kind of scenario?

Regards,
Romain