It wouldn't work today, I'm afraid.
Boeing has got the 727's former market WELL covered by the 737NG series. All routes on which the 727 was formerly the main means of travel, are now flown by the 73G and 738. A large chunk of the 727's high-end market was eaten away by the 757 as well. And of course there's the 739 which although not popular right now, still covers a certain pax range.
Also considering that the 737 Ng series has perhaps the most advanced flight decks to be included on any Boeing airliner, I doubt Boeing would want to introduce a product that would literally fly in the face of this new technology. And the airlines love the 737 NG
, you'd be hard pressed to get sales out of a newer airliner that would essentially offer the same thing that the 738 does, except with rea-mounted engines and a T-tail.
There was also a Boeing executive (one who helped to shut down the 727 production in the end), who once said that he would not allow a new airliner to be designed with a T-tail, as T-tail aircraft are more prone to "deep stall" than normal tail aircraft are.
the 717 was a change from that, but we also have to keep in mind that it was never a built-fron-scratch design on Boeing's part, it's a carry-over from McDonnell-Douglas. But Boeing designing a new airliner, from scratch, with a T-tail, is something you may never see again.
And it's sad because if you ask me, any T-tailed aircraft beats any low-tail aircraft in terms of aesthetics, and in my opinion, T-tailed aircraft give a much smoother, stable flight than their low-tail counterparts. But that's just based on my experience.
It would be neat to see though. The 727 is my favourite aircraft and I'd give my left arm to see a new production variant of it announced. But it just can't happen now.
On the bright side though, the demise of the 727's production line did usher in new improvements to cockpit layout, design, and avionics, on the 757-200 and 767. And those in turn pointed the way to the ultra-advanced cockpits we see today. So I guess there were some benefits and the 757 is a beautiful aircraft. But it's a tough call to say whether the 723 would have had a cockpit similar to that of the existing 757...as I'm sure some airlines would have wanted commonality with their existing 727 fleets. We still would have gotten to the level we are today in terms of advanced cockpits...but it might have happened later rather than sooner.
I'd be very interested to see what reaction Boeing, and the public, would have if an airline approached Boeing and specifically asked them to built them a Boeing 727. A new one, with the promise of a huge order, and refused to take any 737 or A32X product. I bet Boeing would laugh in their face, but I'd be seriously interested to see the reaction of that company...and the world.