Hi!
I think there is nothing wrong if Hardcore stash will be available for transferring items from it to non-Hardcore characters. Or maybe it is already possible with in-game means?
Not possible by in game means.
You can use GD Stash, or rename the hardcore stash file extension (transfer.gsh - I think) to that of the softcore extension (transfer.gst).
As always backup your save folder prior to making changes in case something goes wrong.