Hi,
Let me put it this way, the ageing report requirement comes from client i.e. Business which includes users/core-team members/management.
So, if the requirement to change the ageing report comes from business (whoever is it), then ofcourse, you'll have to rely on them for specifications of report, because ultimately they are the end users for this report, and they know what changes they want.
I'm not sure under what capacity you're asking this question. If you yourself are the user of this report, then you'll have to provide the detailed requirement to your FI guy who'll work with developer to design the report.
Thanks,
Nirav