Scout, Caster, Pet. Which class would you want next?

[Dreadnought]

Bahamut and Odin are most likely like the other major primals : Ifrit, Titan, Shiva, etc.

But, forgive me if I'm wrong, didn't they say that the primals could be summoned by Free Companies somehow? Er, I only read a bit about that part, so I may be mistaken.

yep your right.
im afraid SMN is going to be aesthetically a beast master. with the only difference being the name of the job and perhaps some battle mechanic tweaks as to where SMN and BST have had almost nothing in common in the entire franchise, other than theyre both pet classes.