I am of the opinion that index changes should go through change control. I know in some places it can be big and boxy. I have spent many hours waiting on the conference call for everyone to run through their list of changes to PROD on a change control management meeting before release. I think the undesirable parts of that could be dealt with but it is a necessary thing to have them for index changes. Especially with large data sets they can have implications that you don't want to be surprised by.