It is time to get rid of them SE...

[dinnertime]

I'm pretty sure their point was that it would require them to change and/or rewrite every single job quest from 30 to 52, more if you wanted to extend it to the Flames' anti-primal squad.

I've already answered this in the last line. They can always keep Egi's but overhaul them in gameplay to fit like Demi Primals since that's what people have been asking. That way, they'll only need to add up to the lore instead of rewriting it.
I'm repeating myself here, they've retconned lore before, so it's not impossible for them to change the SMN quests. Lore isn't an excuse to keep things set in stone.

[Taranok]

I've already answered this in the last line. They can always keep Egi's but overhaul them in gameplay to fit like Demi Primals since that's what people have been asking. That way, they'll only need to add up to the lore instead of rewriting it.
I'm repeating myself here, they've retconned lore before, so it's not impossible for them to change the SMN quests. Lore isn't an excuse to keep things set in stone.

Yes, and this is why my favored suggestion is to add trances to summoner all the way at level 4 when you get the emerald carbuncle, and make the carbuncle the summoned payoff during the trance rotation. And then slowly swap out pets as you level. They can keep ifrit-egi as is, or turn it into a demi-ifrit of its own regard and just call it an egi because it's a weaker manifestation than the demis. And obviously at 70 you unlock demi-bahamut, and at 80 demi-phoenix.

If you work the class right, you can keep the egis or carbuncles around in various oGCDs as well. It's not the kind of thing that needs to be outmoded as you level up, you just move away from the permanent poorly implemented pet that is basically a DoT in favor of the better system they want of using oGCDs.

And because we're at it, reduce the total number of oGCDs and rewrite the lore as necessary to fit the new system, which if done correctly will be minimal instead of a complete do-over.