Wrong time period for the Vong, except for a rather obscure quasi reference from the original KOTOR games, they don't belong in the Old Republic and some serious retconning would have to ensue to explain their appearance.
The Mandalorian would feel way too much like a BH except with melee weapons. I like the Echani idea, but you'd have to be careful with the Echani Sun Guard name since they eventually became enemies of the Echani from the other Echani planets, served Darth Plagueis and are the progentiors to Palpatine's Imperial Guard.
heheh. I didn't think anyone else would catch that. I'm sure this would be easy to work around, and so would making the Mandalorians different from the BH.
Do you guys think there WILL ever be new classes? I would have so much fun starting a new character with a new fun story.