I'm not certain how to call the replacement functions, can you provide an example.  I've only tested in IE and Firefox

This is my example Javascript, each of the alerts below display 'undefined'.

            <script language="JavaScript" type="text/javascript" >
            function ShowMyDialog(button)
            {
                //use CuteEditor_GetEditor(elementinsidetheEditor) to get the cute editor instance
                var editor=CuteEditor_GetEditor(button);
                //show the dialog page , and pass the editor as newwin.dialogArguments
                //(handler,url,args,feature)
                alert('editor.Window_GetSavePoint:'+typeof(editor.Window_GetSavePoint))
                alert('Window_GetSavePoint:'+typeof(Window_GetSavePoint))
                alert('GetSavePoint:'+typeof(GetSavePoint))
                var newwin=editor.ShowDialog(null,"My_Custom_Text.html?_rand="+new Date().getTime()
                    ,editor,"dialogWidth:400px;dialogHeight:240px");
            }
        </script>

I looked at the Window_GetSavePoint() function in IE_Implementation\CuteEditorImplementation.js and it has some syntax I'm not familiar with, mainly:
        return
        {
            type:OxO8f05[0xb],controls:arr
        };