Create {{#get_program_data:}} parser function to transclude output of certain programs run server-side.
The programs that can be run and their parameters should be defined in the extension settings. All user input in {{#get_program_data:}} should be sanitised, and the rules for this sanitisation should be configurable in LocalSettings.php.
Programs' output is to be cached in edg_url_cache or similar table according to the extension settings.
Possible use cases: emulating the defunct GraphViz extension, as well as Score or Timeline; importing data from man, etc.