To keep track of progress for this feature request, I create an Issue Tracker for it;
Based on gmoises' idea :
Check his message that dates back to "Tue at 4:00 AM" (and Jaykebird's answers as well).
gmoises wrote :
I suggest a "User" tab where the user can have custom buttons to call external programs.
There is a great example in StExBar, http://tools.tortoisesvn.net/StExBar.html
There should be some environment variables where the user can find the selected files and the selected files' paths.