(New) Summon 3 - Vote for it here!

[Akiza]

I don't get this line of reasoning, Carbuncle doesn't have an element traditionally. Carbuncle in ffxiv has the exact same set abilities as the summon counterparts just weaker. That is likely the reason why the elements overlap as you say, incidentally since they have the exact same abilities their roles overlap which is why Titan and Garuda supersede Carbuncle.
Anyway it's been confirmed that summon 4 and 5 are leviathan and Ramuh, surprising no-one. I hope Levi is a buffer pet and Ramuh a debuffer, only time will tell.

It's not that their roles overlap because Ifit and Garuda are both attacker type pets. Garuda and Titan supersede Carbuncle and Topaz because their attacks overlap.

[KitanaiKoneko]

None of the above. I vote:

5. GabeN

[Dyne_Fellpool]

Gipsy Danger!

[mayonnegg]

Doomtrain.