Visit correction consists in being able to "correct" (add / update / delete) visits already archived, and regenerate reports (archives) for days concerned ( = "targeted days").
Note that regenerate archive reports for "day" period for the targeted days is not sufficient. Week, month (and year ?) archived reports that include the targeted days should also be regenerated ( = "covered days" ).
See [http://forum.piwik.org/read.php?2,75064] for an example.
I think we need to :
The script should ensure that all archives for the associated covered days (in the same week / month / year ? than targeted days) are available (parse logs and archive tables).
The script will then unarchive covered days if necessary.
User should be informed of result / missing information / method (link ?) to recreate specifical archives.