Interesting way to look at it, I don't see a need for the dragon pups as such though. To condense and refine a part of the case I was making a couple years ago, if you accept the FMV cutscenes in Azel as congruent, and as the baseline for continuity: the Dragon even in the form of the Arm Wing reveals itself to possess the essences of the Lagi dragon pup, the Blue Dragon and the Light Wing. I am still more concerned with the mystery of the dragon crests, and my working theory is something like this...
If the uniformity of the crests is to be seen as having significance within the world, then the Blue Dragon can be seen as an archetype. I think they represent some sort of translation portal for the proto-dragon system, which the Heresy Dragon and Sestren are different manifestations of. In this model the appearances of both the Divine Visitor and the third Heresy Dragon in such close proximity to the D-Unit 1 and a Dragon Crest are no accident / coincidence at all. There are three known crests, the first one Edge sees would be the portal the "Edge's dragon" uses to translate itself as a form compatible with the Light Wing essence, or perhaps as an incomplete version of the Light Wing.
The Shelcoof crest is presumably / obviously a portal the Lagi dragon used to both "seal the flying Tower's functions" and translate its own profile into stasis.
The final crest, at the Red Ruins, could be both the portal the Armored Blue Dragon / Type 01 originally used to translate itself into an operational state - which is reasonably consistent with the direction of origin of the path taken by the Eins dragon and Keil - and therefore also a portal that combined with the Lagi crest and the completed Light Wing form can translate all three into a single form combining the strengths and abilities of each of the Heresy Dragon's incarnations. The Solo Wing Dragon.
This is of course conjecture, but it is the one way I see to account for all three dragon crests as significant, at least in general terms. And the pup left by Orta's dragon always seemed like an implicit Phoenix to me, a Dragon Phoenix as it were, which has a certain thematic precedence as well right? 