I agree that since Vader has been sick, that putting him near other birds isn't a good idea. If Vader was strictly kept separate, then maybe. Although, I could only recommend indoors only, until he's healthy and his immune system is built up. Introducing him to the outdoors when he's sick could result in more stress, which isn't good for him. (that is, if the goal of the program is to train him for outside time)
Flight training has nothing to do with the bond you have with your bird. It *might* help, but even having the strongest bond possible with a pet bird doesn't guarantee that bird will come back.