You are right, we don't want to make any one-click add to exclusion list, on purpose.
In the submissions of false positives, we can see the huge amount of users - reporting obvious malware as false positives (and it's not such a simple operation, you have to fill all the fields in the submission window). It's pretty clear that these people would click the "add to exclusions" button, no matter how many warnings would be around that, and execute the malware. So, we don't want to make it any easier - because we believe that this case is much more common than the real false positives.
For experiences users who can reliably say what is a false positive... adding the file to the exclusion list is not that hard (and it's hopefully an operation you don't have to do every day).