Thanks Nick and setting up the Demo isn't an issue much. Would just like the ability to retrieve the files required to do have the demo look like the original, particularly the image files. So even a simple zip file with what is in them would be great. You could even then you could toss up a disclaimer to the effect that the "archived demo files" are for advanced users only, support will not be provided for their use etc.
Sadly not working with the old themes sometimes isn't an option without having to completely rebuild a site. Your own release notes indicate the same.
This version underwent a major design change and code update which means there’s not an easy update path. If you’re happy with your site built on a previous version of the theme, there’s no need to update.
So anything that makes continual work with the old themes easier and more successful is a huge help. You figure over time it would *eventually* fade away but until then...