Currently, it doesn't seems to be possible for an anonymous user to enable any of the options (scripts and/or stylesheets) available through gadgets.
On English Wiktionary, there is the page wiktionary:Project:Per-browser preferences, which complements Gadgets extension and can be used by all users to turn on/off some additional JS/CSS features, even if they are not logged in. Such user preferences are stored in a browser cookie and need to be refreshed every 30 days.
I think the Gadgets extension should be enhanced in order to provide a better user experience for anonymous users in the same way which is currently done on English Wiktionary. Specifically, the extension would:
- Continue to be as it currently is for logged in users;
- Provide some page (e.g. Special:Gadgets, but with checkboxes) where unlogged users could have the chance to enable (or disable, since Bug 13742 was fixed) the tools which are available for logged in users. In this case, though, the preference would be browser-specific (as happens on Wiktionary).
Even if the user needs to refresh his preferences after some time of use (30 days), and every time they change of browser/computer, this approach seems to be a good improvement compared to the current situation.
T22151: Preferences for anonymous users