Options I see:

• Leave it as is, and continue to accumulate hacks. Possibly: modify SecurePoll so poll content works with setlang, set uselang somewhere and pass it around with every request, provide a way for voters to change the content stored in the SecurePoll DB. Pros: If it's not broke, don't fix it. Cons: I'm not sure that condition is true (see the list of bugs above).
• Scrap the custom message system and modify messages through the MediaWiki: namespace. Translations would go at MediaWiki:message/lang for each message and language code in question and would be available through the message system. Pros: Only votewiki admins should have access to edit the MediaWiki namespace, so security should be maintained. Would allow us to use Language and Message as expected. Cons: Unsure how this works on third-party wikis. Probably not an intuitive interface for votewiki admins.
• Scrap the custom message system and put everything through TranslateWiki. Pros: easy to use all around. Cons: Insufficient security?

Thoughts?

I'm more than happy to help with the update though I don't want to tread on toes if there's already something in mind for this.

I'm reading previous comments and honestly, Frances's idea from 2015 sounds very appealing:

Scrap the custom message system and put everything through TranslateWiki. Pros: easy to use all around. Cons: Insufficient security?

I can't speak to security concerns really. I can imagine potentially someone might switch "support" and "oppose" mid-vote or something like that... But I think this risk is outweighed by the benefits. Some I can think of for now:

• Keeps everything in one place like the rest of the production sites
• Means people don't need to translate "support", "oppose", "candidates" etc over and over for every election (or find those translations manually)
• Anyone can translate stuff and doesn't have to rely on people setting up "translation" staging pages on Meta-Wiki (as we do right now for board elections)

I don't know if it's really that simple though especially since some items, e.g. the "intro" text, change on a per-election basis. We'd need to chat through the option to work out if it's really the best approach.