It might be tough, this forum is already a bit creaky (I use the production version of this forum, Discuss extra). But there are a lot of subs that are just sort of there, could you all choose one (like even this one) and take it over for your own purposes?
As far as multilingual, well this forum software handles a huge load of languages already, so why not? Have you tried using your local language to see how it works? All dbs must be utf-8, I guess there is no other way.
Are you in the Balkans? I think Modx can have a lot of potential in south Europe, so many developers and IT companies in the whole region.