If I am right and it is not (yet) available, I would suggest to allow adding an optional 'exception' list that will be taken into account in case of capitalization.
For instance: in case of changing to lower keys, one might wish to keep specific abbreviations unchanged.
Like DVD, USB, SATA, IBM, CD-ROM, etc.
Such items to be saved in a list that can be edited.
Within the rename panel users to tag/untag whether or not the list should be taken into account when renaming.
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The TitleCase rename script is an example of more refined capitalisation. You could extend its set of exceptions to handle the extra cases you want.
Or, perhaps easier, use the build in capitalisation option combined with a simple script that takes the result, looks for the words you want and replaces them with all caps.
Yes, I know, this is an old thread. So far I have 'solved' above matters 'manually', i.e. when DVD is converted to Dvd I manually adjusted that. In case of a couple of files, that is okay. However, it is quite a workload in case of more than just a few files.
(I knew I had touched this subject some day in the past. It took a while to trace this old thread..)
Anyway, frankly, I am not sure how to accomplish what you wrote, not being familiar with scripts.
It would be nice if the script would also offer an option to ignore changing the case of abbreviations listed in a separate .txt file.