Therefore actual message text (and entire portions of the tree) should only be loaded when needed, and removed from memory as soon as possible.

To accomplish that, you could mark the message text variable as 'tmp' and load it on demand rather than when the 'index' object is loaded. To manage that, you would need a way to find the entry for the object in the savefile at a later time. There are a variety of ways to do that if you structure the savefile yourself, but if you let the default Write() do the job for you, it would still be possible if you are willing to take advantage of the way the new savefile format works.

Here is roughly how you could do it:

<code>

var/savefile/SaveFile = new("msg.sav")
obj
   var/tmp/save_dir
   var/tmp/msg
    Read(savefile/F)
      save_dir = F.cd //record where we are located
      return ..()     //load index data
   proc/GetSaveFile()
      if(save_dir)
         SaveFile.cd = save_dir
         return SaveFile
   proc/LoadData()    //load full message data
      var/savefile/F = GetSaveFile()
      F["msg"] >> msg

</code>

Initially, you would load things in with the normal Read() and then later you could call LoadData() when you need the full text.

This technique would not have worked with the old savefile format, because the directory containing the object data existed only temporarily during Write() and Read() and was packed up into a serial buffer at other times. Now you can count on the object directory being persistent.