Automatically defragmenting wallets are something that has been discussed, at least on IRC, quite a few times. As long as miners are willing to bias their priority calculations towards transactions that reduce the size of the UTXO set it can make sense. Not only when you create new payments, but for example at night time if your wallet is open (or on an always-on device like an android).
My point about coin control is that whatever problem you're solving with it, you can usually see a better solution that works for more people.
The benefit of the so called "coin control" for nearly every user is in allowing him/her to see the how the protocol operates "under the hood". This is a great learning tool both for the beginning users and for the developers that begin to work with Bitcoin.
Even if the significant portion of the "coin control" users wont use it for the "control" but just as a magnifying glass to see whats inside their wallet, it will be a great upgrade to the reference client.
Maybe just rename it from "coin control" to "coin loupe & tweezers"?