OmegaWiki has a relevant bug fix; it is now obvious what option you add a part of speech you will see "part of speech" in your own language and when we do not have it, you will get it English as the fall back language. This is a huge improvement from having the same text in some 24 other languages.
The next improvement will become possible when the Multilingual MediaWiki is finished; this will allow you to select the languages you are interested in. These languages are more personal than just falling back to English.
Another option would be to identify a fall back language for a language itself. This makes sense for languages that exist in a space where another language is well known and better supported in MediaWiki. Languages like French, German, Italian, Spanish, Portuguese and Mandarin come to mind.. I am sure there are more..
For the Incubator we want to define fall back languages to make it easier to localise the MediaWiki messages.. We hope to get answers what the best choice is.. otherwise we will have to guess..