An idea I had bandied about a bit was to do this with egis:
- Remove all Carbuncles and Egis as permanent pets.
- When you would get your first Carbuncle, introduce the Trance system immediately and you summon it directly via trances, as per high-level summoner gameplay.
- As you would have unlocked newer Carbuncles/Egis, replace them into the Trance rotation. First Emerald, then Topaz, then Ifrit, Titan, Garuda, Bahamut, and Phoenix
- Define the trance cycle by whatever length you want it to be, though I feel it would be best, eventually, as 4 separate summons on a 2m cycle
- Change all Egi Assaults and Enkindles to instead do temporary summons. Egi Assaults basically call up a pet partially, such as Ifrit's clawing up through the ground and slashing at a target once before disappearing. Enkindle would instead summon 1+ of your replaced summons. It could be random, specific ones, it could be a single one, multiple. It's effectively going to be a DoT but flood the map with more summons, signifying your growth as a summoner to be able to create "Weak" summons effortlessly. But more importantly, it serves as a way for old summons to be seen again.
- As with the current demi-primal system, the demi-summons in the summoner rotation should feel powerful once you become a summoner. They can either have growth as you level up via traits (E.G. Ifrit-Egi->Demi-Ifrit) or just start out in an empowered state, but trances should be larger summons that look more awesome, whereas "weaker" temporary summons can be exclusively the egis or carbuncles, after they've been outmoded.
- And as the final coup de grace, add a bunch of "unused" buttons at various points. These normally do literally nothing, dead space like Enkindle Bahamut is. But when you have a trance running with a demi-summon, they change into unique abilities defined by the pet. They can be GCDs or oGCDs, but are used to customize a minigame of the job's rotation that is exclusive to that trance phase OR primal specifically, giving the class a multifaceted feel that alters depending on what summon is out.
The idea behind this is you basically retool the class around the demi-primal/trance system, but do it from an earlier level. And by making all of the pets temp summons, you can both re-use older pets as well as make the class feel more powerful as a summoner by mixing in a dash of minion master into the class.
Whether we keep a permanent summon or not is honestly whatever at that point, the entire DoT/Aetherflow mechanic can be completely reworked, and you can speed up the cycle. Plus, tying into other ideas I want to see with Summoner, you can make each trance play a little bit differently. One could be just spamming one button over and over, on a simple summon. You can make another rocking 2 abilities with some oGCDs splashed in to spice it up. You can make a third have a 1-2-3 combo, or a 1-1-2 combo, or 1-2-3-4, or it can be 1-1-2-1-1-3 or pretty much whatever you want. It can be as simple or as complicated as the devs want to make it with the tools summoner will have when these summons are not out, and it will fit the Summoner aesthetic nicely.