Well, for what it's worth:
I found the
Universal Extractor, based on AutoIt (runtime included) and utilizing a host of free/open source extractors and identifiers, apparently included.
The site has a high legitimacy value for me; check out the high degree of openness (e.g., open source, support forum, links, other software, tip pages) and history.
The McAfee Site Advisor page for legroom.net says the basic package is okay.
A sufficiency of decision-making info can be found on the main page, with credits and links to the extraction tools. I didn't know that an open-source unpacker existed for InnoSetup!
It's not ideal for this task, however. Here's an option for the extractor:
Warn before executing files - some .exe archives must actually be executed in order to perform the extraction. Since this can be a security risk (executing unknown/untrusted code is always a bad idea), UniExtract will display a warning before extracting these types of files.
But perhaps you can try it and then say no if it warns you. I might do this later, but it's low priority at the moment.