I think I've debated this before, but i don't mind doing it again. I'll step over some of the side-steps you've added (allthough I'm on your side with the white tiger debate, i wouldn't call all zoos that breed them "less reputable").
I'll also step past Devi's weird remarks, how species need to "evolve" within 2/3 generations or else die out!? You can't expect a species to evolve that fast.
So let's focus on the main topic at hand. First of all, I believe that taking in animals gives you the responsability to care for these animals to the best of your ability. In my mind, as soon as individual animals enter your gate the primary responsability rests with the individuals at hand. That does not mean you let animals enter lightly, but you need to highly consider which individuals are taken in, consulting with a breeding programme coördinator.
Taking in animals also include animal births. In my mind, you do not breed animals unless you know you can either hold them yourself, or are able to place them in another zoo. There are enough ways to keep animal populations in control. If contraception is detrimental to a female's reproduction in the future, then why not keep them away from males? For many species you always have the option to give them a contraceptive for a few years, then let them have one birth, and then give them a contraception again for a few years. That way you should be able to have enough room for offspring, without having to kill surplus.
The situation you created gives all the power to the coördinator. Besides the fact that for some species it is unlikely that a zoo is willing to ship them off for free (like a zoo that just bought a few white rhinos in south-africa), let's say this is a possibility. Wouldn't that give the power to the Asian Elephant EEP coördinator to say; "kill your elderly females please, we need to place a few young bulls and your facility can also hold young bulls" and the zoo should do that for the greater good?
Does it also mean that a zoo can't "retire" an elderly tiger? An excellent breeder, that has been a magnificent zoo animal all her life and has bred quite a few youngsters should then, in the situation you created, be authenised because she is no longer contributing to the species survival and holding up space. I don't like it.
Another con;
Who decides what animal is surplus? Is it just the species coördinator, is it the whole TAG, is it a majority of the TAG? Is there any control over a species coördinator, what if he/she makes a mistake? It seems that the decission can be taken quite lightly.
And I would like to add;
Authanasia is by everyone considered to being a fix to a problem. The problem is that there isn't enough space in zoos to keep many species alive. But shouldn't we look at all those zoos that do not participate, that keep and breed animals without considering the greater good of the species. Everything seems to go wrong because people that run zoos don't consider what animals to take in, and generally make a mess. Wouldn't the solution lie in creating stricter European rules to force these zoos to make decent decissions. Perhaps force them to join EAZA and create an European animal police? Create stricter permits to have a zoo (and enforce them)?
Anyways, it feels that this response has become a bit of a mess, but i guess people can get the greater picture. In my mind, Zoos are primeraly responsible for the individuals they hold, and should strictly consider what to take in before they do.