Aaron - what about your project do you think makes it “gnarly”? Based on your description, there isn’t anything unusual about what you’re tasked with. Multiple languages are an aspect of every global enterprise community rollout, and sort themselves out in various ways. In some cases the UI is localized, in other cases the home country’s language becomes the official community language for global communiques and conversations, with local sub-communities popping up using their own language. The World Bank knows a lot about this - they were one of the early adopters of KM approaches back in the 90s!

Slack is designed for much more bottom-up, organic adoption and use, with only very light preconfiguration. As for top-down approaches, as Steven asked, you need to be clear about what the business objectives are for having the capabilities you asked about. There are a number of common use cases for communities, doc sharing, and group calendaring. Which ones are being targeted by WB? And who is the audience? Everyone in the entire organization, or only a subset? This is really KM101 stuff, so if you haven’t mapped out the answers to these questions already you may want to get some help..