Do You want to submit all of them? Or You are asking in advance for further use?
ffmpeg is not so big, using existing dependencies, You can check it using Apps.
One possible way to solve the task is to make an extension, consisting of the script, which being executed builds another (target) extension and places it in the users tce directory. Exapmles are getlocale.tcz and get_mplayer.tcz (from earlier version's repos).