Of all the remaining elder dragons, Primordus and Bubbles have one thing over Jormag.
Both are in near impossible to access areas.
Below the ocean and in the Magma of the Planet.
The Ice Magic of Jormag counters the Fire Magic of Primordus and having Ice Magic against a Water Dragon seems like a good idea.
( It would also make it easier for Anet to create map in the ocean for the potential bubbles fight)
If i would be in the commanders shoes, i would seroiusly think about an alliance.