Actually, a shell is the body and soul, counted seperate from the heart, formed when the original heart and body/soul are seperated. There can still be a heart there: Riku Replica had an artificial heart, and it's looking like the Order members are powered by Elemental hearts. If Riku soothed his heart in Elemental darkness, not only the dark side of the heart, he could very well have replaced it with a dark heart.
This would explain the high NEO's: they are not puppets because they have their own (artificial) heart, their driving force, deep memories, and emotions. The low NEO's (Nobody's), did not have a strong enough heart in the first place for an artificial heart to fit in the new hole, which is why they would need puppetmasters.
When Riku was just a heart (appearing in front of Ansem to stop him in HB), he still had his form, he was just repressed physically by Ansem. Riku Replica, as well, was a shell that had Riku's form.
Unless we are expecting the Order members to regain their hearts and end up looking like the fat shopkeeps from Traverse Town, the high NEO's should look like their old bodies, and, since they retain the soul, retain the conscious memories (knowledge (as in, what I got for my last birthday), but not true memories of the sort in CoM (as in, how my best friend would react if I told them this))
Or maybe I'm wrong, and the final logbook entries are Andy, Larry, Daniel, and Zack (the old forms of Axel, Luxord, Demyx, Xaldane)
And Jacob Twilight: there was another Riku on the path of darkness, in the world of darkness. Mickey talked to him there, telling him that he had the key for "this side". Look it up in a Final Mix FAQ.
However, we won't know anything more until the game comes out. All we know right now is that the only cloaked character in Land of Dragons has a Soul Eater, and Riku has appeared in the cloak (which Nomura says is what identifies the Order) in both CoM and ASAS (possibly also DD, if you think that the GEU is Riku)