I'm not really sure what your idea is.
First of all it was 'why don't they continue the Armageddeon story?' and now it's changed into 'why don't they do Dredd; Year One?', which is a totally different thing.
Armaggedeon was supposed to be about the creation of Dredd's world, up to and including the Atomic Wars in 2070. Since Dredd was 4 years old (although possibly 9 or 10, with accelerated clone growth) at the time of the Atomic Wars, we can safely assume that he probably didn't play much of a pivotal role in those events ;>
And Dredd: Year One? Sorry, but I still don't see the point of it. Batman:Year One was a re-examination of the events that turned Bruce Wayne into Batman, a super-dramatic retelling of the old 'and at that moment a bat flew in the window' myth. Dredd's background doesn't have anything like that. No dead parents trauma, no driven psycholgy, no discovery of the Batcave, nothing.
'I got grown in a lab. I was enrolled in the Academy of Law. I was trained and brainwashed into the hardest bastard on earth.' How many different ways can you re-shape that into something new and mythic and still retain the essence of Dredd?
The only significant event in Dredd's early personal history is his arrest of Rico, which Wagner has already gone over again in the excellent Blood Cadets story. Other than that, there's nothing there that we don't know already.
But don't take my word for it. John Wagner has said before that he doesn't see any point in a 'Young Dredd' story since, as I said above, it would tell us nothing about the chararacter that we didn't already know.