All i found, sorry for grammar i have no time!:
-FF1
one of the 4 fiends of chaos, Tiamat is confirmed, maybe the other 3 too
-FF2
Thancred Skill with Knives is same as Firon in Cg Intro (FF2 remake)
-FF3
Cristal Tower,Eureka, Xande,Cloud of darkness,Amon bosses will appear
Fast Change Class System out of battle first appeared in ff3
Onion Set Armor and Company Crest symbol (ff3)
there are similarty to the intro of ARR and the intro in Cg of FF3 Remake
-FF4
Alphinaud and Rhitahtyn are two Young Mage Twins like Palom and Poron (ff4)
-FF6
I saw That The Yeti boss Umaro will appear somewhere (ff6) (not confirmed 100%)
Primals and Espers Are very similar, both they are sentient and hate humans
The Garlean empire like buildings of "metal" like the Ghestal empire and using "magitek"
-FF7
All the "meteor Crisis" on 1.0 Heavly reminds Of FF7, for months the Dalamud was clearly visible in the sky like last act of FF7
Louisoix before die smiles, same thing done Areith (they are both remembered in the same way by protagonists-Martyr)
Ceruleum Allude To Mako energy, and The coerlum Reactor Allude to the mako reactor, (<<Ceruleum is a refined form of Aether, obtained by draining elemental Crystals of their energy, usually in processing factories. It is a powerful yet highly unstable source of energy, mainly used by Garlean Empire to power Magitek engines>>).
-FF8
The Echo Power works very similar to Ellone powers (live the past but not able to change it)
the Menus Are Grey like in FF8 lol (were blue in 1.0 and old games)
-FFX
The long Change between Astral and Umbral eras (death and rebirth) Reminds of the Eternal Spiral Between The Calm and SIn
The Look of Bahamut is more similar to the one of FFX than the original with long Neck (big torso)
Ishgard Theocracy reminds of Bevelle city(they both are accessible by a long bridge)
Soul Crystals for Jobs as concept are similars of Dresspheres in ffx2 (they are both have souls of dead "heroes"
-FF11
Many Monsters models are 100% from FF11 like Gobbue, mandragora, Ladybug,opopo, Adamantoise, raptor, Peiste, Apkallu.
The Paladin AF gear is The same as In FF11
-FF12
the 5 Judges of Archades are very similar to the "Gaius gang"
the space between areas is delimited by Blue dots like in ff12
Uldah seems like Rabanastre, a Commercial desert city at the center of the map
Cid and his dad worked for the empire, Same was for Cid and Balthier
The party UI is almost the same as FF12, same colors
The Aggro Lines in battle work the same way
Edit: I Deleted Allusion already mentioned in OP