>> Yes, for example in my package's version 1.7 I plan to use
> Hang on a sec — how urgent is this? This seems like a fairly drastic
> step; there’s no problem for me to make a fontspec release on
I don't consider it a drastic step but rather natural – I use other
packages that need to be patched because the upstream versions have
bugs (longtable) or missing features (ucharclasses) not fixed
> But I’d be happy to perform an update by the end of the week if this
> was convenient for you.
This would be nice indeed :-) But there is definitely no pressure
from my side. I now know what to do.
 The bug I'm suffering
is present since more than 14 years, and the patch provided in the
bug report gives better results (although not perfect).
 An updated version should be fixed on its way to CTAN right now.