It's clear that you put a lot of effort into this, but a few nitpicks --
- Blood elves would easily be one of the least likely races to accept a death knight. After what the scourge did to Quel'thalas, the Sin'dorei have a bitter taste in their mouth. Interestingly they accepted the forsaken's aid, but that's mainly due to Sylvanas being their head-honcho and she's good in their book. While the Acherus death knights broke away in a (somewhat) similar fashion, they have no obvious reasons for allegiance to either side, leaving the elves with little reason to (immediately) trust them.
- Worgen death knights are a bit of a tossup, and something I'm not sure about. However, if you've done the new Silverpine Forest questline, you'll see that it's said that if you are either Scourge or worgen, you cannot become the other. That seems to rule out worgen becoming Scourge (death knights) and death knights becoming worgen. If you find a viable way around that, good luck.
If you play a death knight, please, please be careful. Being the guy who hates everyone is not cool and being the whiny angsty guy is not cool. Death knights do have feelings, but their need to kill comes first. Take heed.