I think this is more viable now that the queue has slowed down- it's not as much of a Wow, Skip The Line! ticket since there's not that much of a line to skip. If you'll be added to the site within a day anyways, then having the invite code just makes it feel like a fun personal invite from your buddy (you could automatically follow each other as a result of the code, maybe?) and doesn't negatively impact anyone else waiting for registration too much. Maybe prevent them from being used during times when the invite queue is long...
That being said, maybe remove invite codes and any mention of them if you're not going to use them going forwards, because lots of people have been quite confused about them when registering.
A Strange Cat
Before I start I wanted to mention a couple things -
5 people like this idea