I would presume that there is some form of lingua franka resultant from the Empire, and I feel the need adding voiced acted lines in other languages is not as simple a process as you may think. I personally wouldn't mind the addition of accents in the form of diacritics (æ, ï, ñ, ç, etc.) and eye dialect (been/bin, you/yer, them/'em) to distinguish differences in their speech, as for the addition of extra languages, especially voiced lines, I'm less interested. While I do think it would be a nice addition, I can also see how it could be disliked by some and could be a detriment to gameplay.
If they add accents they should probably create fictionalised ones, taking influence from the real-life factions they are based on. Contrary to what SwadianBorn has posted I do believe you can create a mixture of accents as from my own personal experiences accents aren't rigid and are constantly changing and intermixing with those around them creating mixtures.