1. Dwarves (you all love these bearded fellas)
2. Charr (who whants a pet when you can play like a charr?)
3. Undead (rather smelly but it might be fun)
4. Tengu (my personal favorite ooh i would murder somebody only to play as these little birds)
5. Forgotten (only the snake types the enchanted armors suck)
the only problem would be to make the new armor for them not that hard with dwarves tengu and undead but its gonna be a problem with Charr and Forgotten >.<
Another note where do those races come from ^^ the charr come from even farther to the north so a new map is possible the Desert is a great starting place for the forgotten (not the desert that whe have now but maybe more early in the game when first humans entered the desert) the storyline would have a twist, When playing as charr you dont like seeing a punny human but when you see some undead you think meh let him walk

And last but not least PvP with the new races would be awsome Humans, Dwarves and maybe Tengu against Undead, Charr and forgotten whell what do you think?