This will be in the next build:
NEW: Added a television option "If a recording rule does not include post-process tagging or command, apply respective defaults."
If you are going to use the same command for all recordings, you will not need to edit all your recording rules. Just save a default, and turn this option on.
It is important that you note the difference between "a rule has no command set" and "a rule has an empty command". Rules that were created in MC23 and earlier have no post-process command. For such rules the default command will be used if the option is turned on. A rule with an empty command is one that is created in MC24 (or created earlier but edited in MC24) with the command line string empty. Such rules will not have any command executed.
Similarly, any rules that were created after the "Apply these tags" feature was introduced would have a tag string saved, even if such tagging properties were empty. No defaults will be applied in such rules. On the other hand rules that had been created before the "Apply these tags" feature was introduced, and have not been edited since, will not have any tagging property in them, and the defaults may be applied.