What alternatives do I have to use the Computed Field module?
Using rules you can do basic calculations with field values and write the result into an other field. If you do the calculation after an instance of your content type has been saved you make sure the value is always up to date.

Of course you can implement your own action as well and hook it into rules. See hook_rules_action_info.

Whether your users find rules easy to manage and you can trust them to give them access to the rules system is an other story. Depending on what you want to evaluate you might just add some fields to get all the information you need and add a custom action to do the evaluation.