So a lot of people in this thread are completely misunderstanding whats been asked for.
To use a few examples across different jobs, starting with Black Mage:
-Fire IV and Blizzard IV are mutually exclusive. If you can use one, you cannot use the other. I would like an option that allows me to place those 2 separate abilities into one Hotkey. Their use remains identical to now, I just press Q for Blizzard IV in UI and Q for Fire IV in UF. I can then move Triplecast to E and not have to use Shift+MouseButton5 to use Triplecast.
Rotation = Identical.
Button Presses = Identical.
Unique keybinds = -1
=Space on hotbar saved, one less keybind required.
Dark Knight:
-Blood Weapon is mutually exclusive to Blood Price. I would like the option to have Blood Price activate on Q when in Grit and when Grit is off, Blood Weapon is on the Q bind. No gameplay changes, I just didn't have to press Shift+Q for Blood Weapon when Grit is down.
Dragoon weaponskills are not combos, they're Chains. Both chains have a unique starter and a unique finisher, there is no branching. I would like the option to layer True - Vorpal - Full - FaC into one keybind. Same for Impulse Drive - Disembowel - Chaos Thrust - Wheeling Thrust.
I would still be using the individual jumps between each individual keypress.
Pressing 2 after 1, 3 after 2 and 4 after 3 isn't any more or less demanding than pressing 1 four times. I can still accidentally hit ID before finishing the FaC/WT portion and reset the chain that way or fail to use an oGCD between skills.
All it does is reduce the number of unique keybinds I need to use to achieve my rotation.
Warriors already do this naturally with Fel Cleave and Decimate. Its a system proven to not interfere with Warriors gameplay, nor dumb down its skill list or do any of bad horrible things some people in this thread believe will happen if skills with identical usage limitations to Fel Cleave and Decimate get a similar treatment.
Not once have I or anyone else wanted to "dumb down" or simplify jobs into mashing a single key for the entire rotation. All I want is the ability to choose to layer mutually exclusive skills into singular keybinds. Nothing needs to be 'lost' to enable this kind of layering and switching.
Once again, I want it as an OPTION. If you feel that having Fire IV and Blizzard IV eat two separate keybinds, go ahead and do so. Meanwhile, those of us who feel that such mutually exclusive skills should be on one keybind, we can do that.
If you like having every slot on your hotbar filled with skills, go right ahead. I don't and would like the option to not.