It actually would be quite a lot of work to do... Carbuncle is easy enough, they're pallet swaps, Carbuncle has both Tank and Mage movesets, they'd just need to give him animations for Melee and they're basically done there.
The Egis, though... Well, if they're working it how I think they're working it, they need to give each Egi each moveset. Ifrit needs animations for Tank and Mage. Garuda needs them for Tank and Melee. And so on. That's the only way I can see Egi-Glamours going down well, if they keep Garuda as a Mage, and just go "But you can have Ramuh as Mage instead!", then that doesn't address the underlying reason Egi-Glamours are desired... Titan and Shiva could be Tanks, for example, but I want to use Shiva-Egi! I'd never get to see her though, because Tank-Egi is never really used... The only way to really give us Egi-Glamours is to say "Pick an Egi, and all three of your summons will be that", or something similar. Personally I'd opt for using that unused offhand slot Summoner (and every Job that isn't Paladin) has. Unlocking Arcanist gives you a Ruby Gem to equip there, makes your pet Carbuncle (whether they want to bother with Topaz/etc. as well is up to them). The Summoner quests reward you with Inferno/Tremor/Vortex Gems for their respective Egis. Equipping the Vortex Gem means you only summon Garuda-Egi, be that Tank, Mage, or Melee version. The remaining Egis can then be obtained somehow. All they're really need to do beyond that is lock the Summon skills behind having a Gem equipped, the same way Shield Bash is locked behind having a shield equipped.
Basically, while the models for some of them already exist (Ramuh-Egi, for example), the animations do not. That's what is taking up most of their time. Ramuh-Egi perhaps has a moveset for being a Mage pet, but for Egi-Glamours to work properly, he needs moves for Tank and Melee. That's what is taking so long.
I kind of hope they keep Enkindle special though... Rather than Ifrit getting a Mage and Tank Enkindle, I'd rather see all of them have their own thing, with Enkindle being rebalanced to prevent one of them being the best. Though ideally I guess I'd like them to be situational... This game lacks Healing Ruby... Wonder is Scholar can get Carbuncle as well...