As much as I want to add more summons, arguably that is not what the job needs. The reason DT SMN landed so flat is not simply because Solar Bahamut is another Bahamut but that it changes so little to nothing.

The rotation is still Demi > Primal Gems x3 > Demi > primal Gems. Whether Solar is every other is immaterial because it adds nothing at all bar a different graphic.

What the job needs is a change to its core mechanic. Whether that is how gems work, or the rotations of each phase either could be good. It fundamentally needs something to build up towards. Something to manage, and more cast times. Heck at this stage I would cast off the differentiation between Demi and Gemstone Primals and have them all linger, just do different things.

If you had to build up to Solar Bahamut, it would have much more impact. But it doesn't. Your suggested change, while would shake things up a little, play into the roles basic issues: The illusion of choice. But as the impact of that choice is so minor, it leaves the job feeling stale.

I do think the rework conceptually is good. I just think that the implementation is problematic.

No job should be "braindead easy" to facilitate learning mechanics.