I would suggest that at LvL 80 when you have done the story line all the way out, you should be able to have the option to change your race. For a cost.
Some people will be unhappy of how the character ends up looking like at the end. Like me, I play a Charr guardian. I really liked the story but at LvL 80 I found out I really really really hated how the Charr ended up lok like with the end game gear.
And not everyone have the time to play up a charater to LvL 80 ones a week.
Some would say that it reduces the replay value if you could change, but I will disagree.
First of all, how many times can you play one class without having to play the same story over again? 20? 30 times? How many people have the time to play each race 30 times to LvL 80? I would say none.
If someone have played through one race and changes to another, that will not stop him from starting to play that race with a new class. The replay value of the game is the story and classes.
If so, make it cost “diamonds” to change race. And while we are on the “change” subject. Lets get the options to change our looks too.
Lost where no man has been lost before!