I think it would be a great idea if you add an option for the user to select whether they want Autosave on a certain time period (for example, every 30 minutes) of their progress in Builder/Upfront. The autosave function would create a backup with a different name of all layers where the user could have made changes: Custom CSS/HTML, Element Settings, Page (Layout) Settings. Afterward, if disaster happens, the user can access his last 5(10,20?) autosave versions and can choose to revert. I believe this will save a lot of wasted time and nerves of all Upfront users and it will be greatly appreciated.
I hope you take this into consideration.
To all members reading this: if you like the proposition, please support it so it attracts the attention of the developers.