Basically, Aion.

For those of you who don't know what I'm talking about, in Aion (MMO) you have chain skills kinda like in FF14. However, when you use the first skill in a combo, that skill on the hotbar turns into the next skill in the combo for a limited time. Thus making it far easier to manage your hotbar because you aren't clogging it with 2 combo chains.

For example, as Lancer :

You have True Thrust on your hotbar for key 1. When you use it, key 1 turns into Vorpal Thrust. When you use Vorpal thrust, key 1 turns into Full Thrust. Once you activate Full Thrust, the key turns back into True Thrust.