It is possible to change any unit's type of aircraft using the timetable feature, but is it possible to change the active unit using timetable? 

 

ie, lets say the player is in 77SQN RAAF flying Spitfires MKVs in the excellent Darwin campaign and is currently at Sattler's AF, can he be "posted" or "transferred" to 75SQN RAAF flying Spitfire MKIIIs at Darwin AF?

Obviously I can do this in the squadron editor and generate a new mission and it will take effect, but I wan't the generator to do it in campaign at a certain date, with a nice little message explaining the brass' reason for transferring you out of your cushy little posting to the front line

You could do it through the timetable by renaming the unit and changing the plane type at the same time.  And a message explaining your transfer. You'd still have all your current squad mates though.  (But I could add some command to change them all up too....)

The timetable is a wonderful tool to make even dynamic campaigns more immersive. Any new commands to allow campaign makers add extra layers of flavour to their work are always welcome.