Glad to hear you like the achievements system. You can indeed re-add the defaults if you wish, even after upgrading. If you look in the following folder on your server, you will see the 3 xml files which are used to add these. You can use these files with the import button in the relevant areas. Of course, import ranks and badges before you import the rules
\applications\core\data\achievements
Once you have done that and made any adjustments you would like to make, you can then use the rebuild button to rebuild for all members on your site
Hope that answers your question, but please feel free to shout up if you have any further questions on these