Hello till and thanks for your reponse.
So what you mean is to create a new plugin here: (just an example)
Here I will create all the functions (install, uninstall a drupal/wordpress/etc to a client) to manage the "universal package installer format"?
Some UI will be useful as you said to manage that.
Then with the remoting class, I just add a new record in the DB saying "I will create a drupal site in the site id = 1".
And finally the server.sh cron file will be executed and install the site.
Thanks for your feedback in advance.