Ability Combo Option.

We already have it for PvP.
Hien has it when you play as him for that quest in Stormblood.
An option to engage Combo's for us PCs would be real nice out in ordinary gameplay too.

Of course people are gonna say "Git Gud", "Learn to Play" or "That's overpowered" or something. Ok then so we hinder it. If you press the button while the GCD is on then it resets the combo and you start over. So you have to time your button presses carefully. There, no button mashing. And due to human reaction time, it's not perfectly optimal for high end play. Although high end play is still possible with the set up.
It's not auto-mating combat or botting anything out at all. Just instead of the same 1, 2, 3, 1, 2, 3. It's just 1, 1, 1. instead.Not counting weaving your OGCDs in there.

And as a bonus it helps lighten the intense button load of classes like SAM or MNK.

It's not an invalid suggestion, though I wonder how they would do the existing combos right now that have branching paths, like WAR, PLD, or NIN. I would really like this as an option, though, especially for GNB where I feel hard to justify wanting 4 buttons for combo I can only use twice in a minute.

I would at least like an option to show you your next combo step on your HUD, like some other MMOs with combos have. If you are reading this and say "Well duh, what's so hard about hitting three options in a row?". It's actually more a thing in games like this where there's a lot of things that drown out sounds, animations getting cancelled, floating text being overloaded, where you can lose track of what parts of your combo actually went through. The solution for me right now is, despite most of my GCDs being hidden, I keep the second and/or third step of a combo somewhere on my HUD and make it big, so I always know what input has gone through. That said, I'd like some kind of optional way of displaying the next step of a combo irrespective of the HUD.

Anyway, I would like compound buttons. Some people like having the separate buttons, which is valid, too. Thus I'd like it to be something you can opt into.

Yes, as I did say it would be optional. Depending on how you wanna set up your hud.

And for your 'problem' again PvP.
War has two single target combos and one AoE combo yes?
Your issue is that Storm's Eye and Storm's path start from the same root ability.
Well two combos = 2 buttons. while the first in the combo is going to be the same button doesn't matter which you hit when it branches the two different paths will be on two different buttons and thus you choose which to press to finish out the combo.
Just like in PvP.