exclude tax from discount calculation at the supplier site level?

In R12

We have a need to exclude tax from discount for some suppliers and others to include tax from discount for other suppliers.

The ideal solution would be than the option: Exclude tax from Discount Calculation which is prensently available in Payment Payables options,would be available at the supplier site level.

Would you know if this is a functionality that will be available soon.

We could change created another discount rate that would be reduced to make the same effect, however this will proliferate the number of discount rates because of different tax rates.

Would you have other solutions.