Sorry, don't think I can vote for this one.  We are not hosted and the programing required and data space that saving everything that was deleted could be immense.  How long would you keep it?  What happens if you restore it and data on records has been changed?  I think one could end up with a huge, huge mess. 

If you accidentally delete/change something major use your backup.  We've probably all over the years deleted something and had to re-enter.  Unfortunately, it's part of the learning process.