That's a very specific batch process! However, in the upcoming release of the IconDeveloper v2.0 beta (currently only available to ODNT subscribers), there is a way to achieve this in two batch processes. First, you can export the images from your icons to a folder. In this process you can select just certain images as opposed to exporting all of them. You can make your selections based on size and bit depth. Secondly, you can do a batch creation of icons from the images you exported. That should do the trick!