IDoc flat file to IDoc

I am receiving flat file in SFTP Server which need to be posted into SAP (No mapping involved)

What will be the best approach ?

1. I tried using IDOCFlatToXmlConvertor (The limitation in the format of source file. The parent and child node relationship should be explicitly mentioned in IDoc flat file which legacy system is not able to do) - Any workarounds ?

2. I moved the Idoc flat file into SAP application server. Now need to schedule job using program RSEINB00

3. File Content Conversion

Any other better solution ? Appreciate your help.

Thanks and regards,

Jose Augastine