The devs have said they want to focus on job identity in 8.0, so now’s the time to put out ideas! While I like the idea of building up to demis, my concern is that your setup would pair one gem to one demi, and make it harder to add new summons in the future, as it disrupts the current triad of gem summons we have now. And one of the things most SMNs have been begging for, for years now, is more summons.

The idea I prefer that I’ve seen a few people propose slightly different versions of is essentially this… first and foremost, add in Levi, Shiva & Ramuh, with their own unique spells & animations. Then split all 6 gems into their astral and umbral teams. We have a Solar (Light/Hydaelyn) now, so we’ll probably get a Lunar (Dark/Zodiark) for balance. Then give us a button, similar to BLM’s Transpose or PCT’s Subtractive Palette, that switches between the Astral and Umbral teams, changing the gem summons (and their respective buttons) to their appropriate groups. So you could pick which team you want to start with, depending on what type of mechanics you’ll be dealing with.

So the eventual rotation could look like:
Solar > Umbral Gems > Bahamut
Lunar > Astral Gems > Phoenix
with the option to start in Solar or Lunar.

Or if you prefer a build-up to the bigger demis, maybe:
Bahamut > Umbral Gems > Solar
Phoenix > Astral Gems > Lunar

Although I figure it would probably end up being the first one, since all the big damage is in the 2-minute window, and the devs seem to be keeping to that, at least so far. They’d have to make both teams pretty equivalent potency-wise, so that it’s not a DPS loss to choose the “other” team, but better to choose one team over the other just due to mechanics. But keeping the gems as triads (even if they would need to be rearranged slightly to fit their teams), leaves it open for more triads/demis to be added in the future without a ton of extra buttons. Either way, it seems like a fairly long rotation, but at least it offers a lot more variety to it than what we have now with:
Solar > Gems > Bahamut > Gems > Solar > Gems > Phoenix > Gems

Honestly, they could just add Levi, Shiva and Ramuh, without any fancy astral/umbral rotation and I’d be perfectly content at this point. I like the rhythm of new SMN and it flows well. This is just what my ideal would look like.