Standard practice among wiki communities, most notably Wikipedia, is to have separate sites for different languages. There is an en.wikipedia.org and an nl.wikipedia.org, and while there are some connections between them (same technology, use of Wikidata, shared governance...), they are, by and large, separate projects with separate communities.
A Wikipedia-style solution will not work for many Wagn sites, many of which are intended to support one set of unified data in multiple languages. For example, consider Wikirate.org. As the name implies, quantitative data is quite central to WikiRate, and rich, nuanced interactions with quantitative data are core to what we are trying to achieve. Many of those numbers (eg transparency scores and voting that feeds into them) are based on micro-interactions on the site, and our vision of transparency for those numbers depends on our being able to see exactly where they all come from.
All of this means implementing WikiRate's vision on separate sites, as Wikipedia does, would not work. We do not want companies to score differently in different languages, nor do we want to multiply a company’s' reporting overhead by asking them to respond to the same questions on multiple sites. We don't want transparency scores to be based on separate sites that users can't see. Perhaps most importantly, we want the world-wide community of wikirate users to be able to speak with a unified voice in pushing to "make companies clear" and to enjoy facing the cross-cultural challenges of working on this together.
The following issues are problematic even in monolingual (non-English) contexts: