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. Your cutscene retcon is not a good solution to this when players undergoing these quests are going to expect to actually see the Egi all the time, and you imply that you want to update the Demi-primal models to better represent the primals during DWT anyways in points 2 and 3, so there's no real reason to change the Egi as they currently are.
Beyond that I'm fine with this. I've discussed my other problems with your thoughts on SMN and Arcanist in the other thread too, if you're interested in that. I think it might be a good idea to bring some of that information into a separate thread, but the relevant beats on why SMN has to keep what it has now would be useful here.