It was obvious that blockchain.info would "help" MtGox out. The actual Bitcoin developers, on the other hand, basically responded by saying "You actually don't need this new txid thing you demand, just code your damn php based bitcoin daemon to look at actual inputs and outputs".
https://github.com/bitcoin/bitcoin/pull/3656Hey, another ID could be useful to help with customer support— really this is only because people are not using Bitcoin as intended: if all your withdraws were to unique scriptPubkeys then thats all the ID you need to know you've been paid.
Of course, there would be no reason to gate withdraws on being able to give people IDs to look up transactions: For one, you could always have your own internal gox UUID (which they already issue) to list-of-txids. ... and even without _any_ improvements in that regard, an ID lookup is only relevant in some negligible number of odd transactions. I'm pretty sure customers would understand "Withdraws are enabled and working fine, but if there is any issue with your transaction, you'll have to wait in a long support queue to get it sorted" and prefer that over the current situation.
What that additional ID has to do with the Bitcoin protocol I dunno— it would purely be a frontend feature, and it's not like bitcoin-qt is the most significant wallet frontend— esp since it doesn't normally index third party transactions at all. There is no place for something like that in the protocol itself, similar to how the protocol itself has no concept of addresses (only scriptpubkeys) or change.