Is aviation software translated into the users' native language desirable over English?
English is the native language of aviation... 
I myself always get mightily annoyed at poorly translated software, which is 90% of all software provided in multiple languages. IF you provide multiple languages, allow the user to switch between them AND get professional translators to do the work.

Would it sell? Probably, if it's good enough. But I don't see the language options as being a major selling point. Certainly not so big that having them will make a large number of potential customers choose it over another product that has more options elsewhere but lacks language selection.
In some places maybe, where English is less than common and not generally used by ATC.
Whether that's where your intended market is I don't know.