Would it be possible to source the current from a second source? Mercator Ocean has proved to be much better than the NOAA source over the past years.

The NOOA model sometimes gives unrealistic data (example on this screenshot). We have compared both models during many sailboat races in the Gulf Stream, in Asia, in the Anguillas current and Mercator Ocean has always been the best model offshore. Mercator also has the My Ocean IBI model for Europe which takes into account the tides. Both models would be a valuable input for Windy. They are free.