I'm leaning toward transferring Billy (with later canon update) and Mace would be straight from canon.

Ohhhhh man, Bellamy. I hated him for about two seconds, but then his bravado begins to crack and we see the scared boy underneath (especially when he's challenged by Clarke). Then there was his back story episode and the hallucinations and I was GONE. Add to that all the difficult decisions he's had to make (as have all the kids), and that was it. Done. Queued. XD