Thanks for the suggestion. I think what you're after is already available when you're 'sending' files, if you click the 'File Server Region' section on the send form you'll be able to switch to say Europe before you add the files. Obviously once you start uploading the files they are locked to the region that you're uploading to...
This feature isn't currently available for 'Share files' because of the quicker workflow. It's something we can look but there's a few complications that could make it a little tricky...