To add on Currency Exchange: Company

Hi all,
If you have multiple companies setup and not all using the same RATE or the same source (Bank) for getting the Exchange Rate.
Ex. Source Bank A or B or C depending on the number of Companies.

Should not we have a field Company (Not as required) so Rates are created per Company and if not filled means this Rate will be used by all Companies?

Ex. Company A using Bank B and Company B using Bank Bank C while Company C is using Bank A
Ex. Single Bank is being used by all so No COMPANY is selected on the Exchange Rate.

Just a thought.