I have successfully got this to work. What you can do also instead of having to republish the entire OS, is open the publisher and do an OS image. Then just point it to the media msi. (I know, I know this doesn't seem like it would work, but trust me it does). It will then just create the media published to the CSDB.
Now all you have to do is go into your OS, and change the OS media name to point to the new name of the media you just updated. Now you have the new media attached to your existing OS with all your install.ini changes. :) Saves a butt load of time if you don't have to upload an entire OS all over again just to get the new media updates applied. Good luck!