Default Card for currency

I’d love to have a feature, where I can select a default card for each currency.
For example I would like to be always charged onto one card for purchases in $, but on a different card for purchases in Euro and a third one for GBP.
This would help me not getting hit by FX rates on the weekends for example.
With some companies you don’t know when they charge you, but a default card could solve the issue.

There is another popular idea for a solution to the problem of unnecessary FX in Curve, which you may want to vote for: