Run the starting cutscene script at the beginning of the mission instead of the intro. Run the ending cutscene after all objectives are completed and have it trigger the mission ending when it has played.
This prevents the players from doing anything stupid during cutscenes:
Code:
disableUserInput true;
and when the cutscene ends, allow them to start fighting again:
Code:
disableUserInput false;
Note that the only way to get out of the game during that is Alt+F4, so MAKE SURE that whatever happens, the disabling command gets executed.
Even if you don't do it this way you can just copy-paste stuff between the Intro, Mission and Outro sections, and all will be the same.