Kic00 on "tinyMCE upgrade in 3.9 broke javascript in a plugin"

Hi - the WP upgrade to 3.9 broke a plugin we are using (which isn't supported by its author anymore).

The lines of javascript that broke were lines where the author was trying to override the wpeditimage plugin to tinyMCE with this line:
tinymce.plugins.wpeditImage.prototype._do_shcode = function(co) {
...
}

That line returns a TypeError in the console:
TypeError: 'undefined' is not an object (evaluating 'tinymce.plugins.wpeditimage.prototype')

Is this sort of monkey patching no longer possible? Or do I need a new path or something? The console also isn't showing the wpeditimage object at all as an addressable entity.