Pass copy of current field data to mapper

We need to pass a copy of the current field data to the mappers. I have came across two mappers where this is needed:

1. File mapper
   • When we return a blank than the current image will be removed.
   • https://drupal.org/node/2049341
2. Taxonomy mapper
   • When we return a blank than the current terms will be duplicated.
   • https://drupal.org/node/2033519

This is pretty closely tied with: https://drupal.org/node/1107522
Do we create a separate patch for this issue or do it in the framework patch? (https://drupal.org/node/1107522)

Another thing is, which way would be take this? Do we just send a complete copy of the current entity to the mappers and let the mappers handle getting the current field value, or do we do it in FeedsProcessor and only send a copy to the mapper so that the mapper get's it's own field value and doesn't have to do much more logic? I am willing to create a patch, just would like to know which way the maintainers want to take.