1. the problem is OP, u assume Midgarsormr's form is "unique" among dragons. not to mention the serpentine wyrm on Heavensward logo have a pair of hind legs, which i doubt Midgarsormr have it because it didn't showed up on his corpse
2. if u guys really watched the stream, theres a section where all that left inside final coil3 end is Bahamut's head and neck, no torso mind u. Thats quite a high possibility that shutting down the 3rd beam engine disperse Bahamut back into the aether /POOF