Hi Pradeep,
I understand your concerns. Unfortunately I'm not an ALE expert, so I can't say, whether the FILE port can be customized or modified or whether there are any other "user exits" in the ALE layer that can be used to achieve your requirement.
(However: SAP BC is not "another sap system"... It's only a small component that can be installed in 10min. Perhaps you can try it out in a test system as a proof of concept and then decide, whether it would be too much effort for your client or not?!)
Best Regards, Ulrich