Demi-Summoner Idea

[Kalise]

I didn't. The Carbuncles, while nice, are intended to be replaced by the Egi as part of the SMN questline. Their abilities see potency upgrades to reflect their enhanced power baseline. We literally gain the Aether to summon Ifrit, and then replace Topaz and Emerald Carbuncle's vessels with Titan and Garuda respectively.

Please, if you're going to write fanfiction, keep it out of actual discussions.

Nowhere in the lore are Egi's relevant to Carbuncles and our ability to summon them.

The only "Upgrade" is a mechanical one to just simply remove the ability to summon Carbuncles and "Replace" the Summon I and Summon II skills with Garuda-Egi and Titan-Egi.