InDesign server adaptation of script

It's all much simpler, should have thought of it earlier. Create an object style, set the size and position (and whatever else) in the style. Then this two-liner is all you need:

index = app.documents[0].indexes[0].generate()[0];
index.textContainers[0].appliedObjectStyle = 
  app.documents[0].objectStyles.item('Index');

(You could actually do it in one line, but it'll be long & unreadable.)

It's more robust (in my opinion, anyway) because you don't have to work out where to place the frame, how to size it, set columns, etc. It's all determined by the frame on the master spread.

As for updating the index manually, that's easy to do:

- Delete the index story (leave the frames): Ctrl/Cmnd+A, Del.

- Generate the index, place it anywhere on the same page as the (now empty) first index frame.

- Thread the newly generated index frame to the first frame of the index story

- Delete the generated index frame.

A simpler and more robust approach is to add a text frame for the index in your template and override it when you generate and place the index. Label the frame 'index' on the Layers panel, then after you override the frame, you do this (works in ID Server and ID Desktop):

// Find the target frame
target = app.documents[0].textFrames.item ('index');

// Generate the index. The function returns
// an array of stories
index = app.documents[0].indexes[0].generate()[0];

// Get a reference to the frame, need to remove it later
indexFrame = index.textContainers[0];

// Move the index story to the target frame
index.move (LocationOptions.AT_BEGINNING, target);

// Remove the frame that the index was generated in
indexFrame.remove();

AFAIK, in IDS you can't use Clipboard - copy / cut / paste - but location as (x, y) should work perfectly fine.