How can I extend drush aliases with specific variables? I like to know if it is possible to extend drush aliases with more specific path variables. Is there anybody who can tell me how to extend the drush example code, that follows below with array for the file system paths for 


temporary files directory
files directory
private files directory


So that I don't have to change them manually after every db sync when the dev server has other path settings then the productive server

This may be a silly question but I just looked at the documentation on github and haven't found any details.
The Drush rsync and drupal-directory (dd) commands already supports the functionality you desire, without the need for you to extend your alias files.  For example, to copy your files directory:

drush rsync @live:%files @dev:%files

To copy a specific folder from your temporary directory:

drush rsync @dev:%temp/foo @live:%temp

To change your working directory to the location where the devel modulr is installed:

cd $(drush dd @dev:%devel)