This is a small script for completely removing all references to missing plugins from your 3ds Max scene.
Use with care (!) and do not save the results under the same file name!
The script will replace any missing plugin object with the first usable alternative object of the same class (e.g. a missing render effect will be replaced by the first available render effect). I cannot give any guarantees this will not mess up your data, your machine or your live.
To run it, just open the scene that reports missing plugins and run the script by drag-and-drop or through the MAXScript > Run menu.
In the MAXScript listener, you can find some additional information on what was replaced.
Minimal testing so far - please let me know if it works for you (or not), thanks!