Using the information we've got from the game, wikis etc. We can make the full language of dragon, just get words and use them to make new ones to create a full language all Dovahkiins will use.

Seems a lot of effort for the end result.

What about Dragon Slang?

I'm not sure just how relevant you'll find this, but I heard that if you translate what the Draugr are saying, they're actually apologising for attacking you.

LOL

So actually he/she would say:'''Don't think it is personal, but i have to kill you because you are not welcome here...sorry D:''

More like. "Well we would have left you alone and all but you attacked us first and stole our [censored]."

Well, they're supposed to be thralls of some kind, aren't they? I think it would make sense.

http://elderscrolls.wikia.com/wiki/Dragon_Language

Are those the guys that are like glowing ghosts that keep saying I'm sorry?

Nah, not really. You could interprete it like that, since they essentially say "Eternal Sorrow" (Unslaad Krosis), but they also say "Doomed dragonhunter" (Daanik Ah Dov), and I'd think the latter certainly isn't an apology. I've actually always interpreted Unslaad Krosis as "eternal sorrow upon you, intruder"

Aren't those the thralls? They often say "Thank you" when you kill them ...