Need suggestion Source multiple files -- > 1 IDOC

Hello Friends,

Good day !!

I am looking for a good design approach for below scenario.

I have 40 source system, all send material files as text and couple of them as excel. Overall there are 25 target fields to create an IDOC.

Unfortunately, all source files do not use same file structure. Source files are varying in file structure as in using fewer fields or all fields.

Do I need to create 20 different mappings, as the file structure is varying?

Could you suggest some best designing to build.

Thanks in advance.

Hari