Since the main idea behind this proposal is simply to avoid confusion with acronyms commonly used in the local language, I would support simply adding S to form WIST, CIST, and EIST.  This would be a relatively simple change as, although the four Indonesian zone IDs have shifted offsets several times, it does not appear that any have used DST in their historical entries.  This would meet the goal of disambiguating from conflicting local acronyms to the benefit of Indonesian-speaking users of this database, while still maintaining readability to English-speaking users.

Of course, the actual display of such abbreviations in any production software would remain largely an issue of localization.