The thing is about an "Ultimate DC" universe is that Marvel.... well, they did it first. And quite successfully. If DC ever did something like this, EVERYONE would know that DC is doing a blatant copy job of what Marvel did/is still doing.
BUT, I love the idea of an "Ultimate DC" universe. I grew up a Marvel fan and didn't really read DC comics. I'm a huge fan of the DC characters(thanks to the DCAU. Thank you WB!), grew up with the Batman and Superman movies, but too many DC books, and not enough time and money keep me from buying into those. But if DC ever did something like this, it would be a great way for me and many fans to enjoy new versions of these characters with new beginnings of sorts.
I would totally dig something like this and I would buy it. I honestly think maybe at one time the big wigs at DC thought about doing something like this, but I honestly think too that they nixed the idea of it for it being a straight up copy cat job of what Marvel did. In a way it sucks because someone else did it first, but at the same time it still would be a neat idea to do.
The Clown Prince