On button bloat:

I would be a huge fan of stacked slots, and with how the combo system works they would be straightforward and could cut 3 or more keybinds from almost every melee job. Monk is still the odd duck because its combos work differently, but if they could be combined with buffs, perfect balance in this case, then combo abilities could generally be executed with 2 keybinds instead of 6, even though the other abilities would be available somewhere. And of course, a significantly more robust macro system could accomplish everything mentioned, but may be harder for players to use or learn.

If I'm understanding the Cycled/Radial/Quick-bar Skills mention right, you would need to enter 2 key commands to execute the action, i.e. pressing "1" then "1" for summon I, or "1" then "3" for summon III. It's not 100% clear to me what is being suggested. Of note, this is similar to one of the additions to cross-hotbars they added where you reach a set hotbar by pressing R2->L2 + key and L2->R2 + key. Instead of going to a static hotbar however, it goes to a sub-listing for that keybind. This would be handy for a variety of situations, though I see primarily stances and other not-often-used skills as the easiest targets for places hotbar bloat could be reduced.

On the skill gap:

I have a sort of "you can lead a horse to water, but you can't make it drink" opinion on in game information. On the one hand, I certainly see no reason not to include more and better documentation and tools about each job, rotation, ability, buff, and debuff. On the other hand, I also don't think a majority of players would use it except when it is convenient for them (this mentality is even probably one of those "contradictory community expectations"). A training room would be great for people that want to improve but unused by most that believe themselves to be playing "good enough." Statics and some PF groups would get use out of it, but in DF and a majority of PF groups, this would not be the path of least resistance.

On gameplay changes to reduce the skill gap however, there is truly so much that can be done.
I'll preface this with the fact that I don't believe any of these sorts of changes are likely, though I would happiliy be surprised, and that I feel this goes beyond UI-level changes. Also from what the devs have said, changes of this sort won't happen with 4.0.

Many cooldowns could be reduced to a trait, and power surge is a great example. Power surge could then either make every other Jump hit for 50% more, every one hit for 25% more, reduce the cooldown, make Jump and Spineshatter Dive hit for a portion more, etc. One thing I learned that some abilities in WOW do is activate automatically. This happens with self-healing abilities and the like in particular, but could also apply to lifesavers like Living Dead and Holmgang. Many reactionary abilities and "always-use" cooldowns could be modified in a way that either actually or effectively activates them automatically. Most changes of this sort would not appreciably change gameplay, but would reduce the number of keys to press and keep track of.

The other thing is procs. FFXIV does have procs of various sorts, Bloodletter, half MP Medica, free Esuna, double power Scathe, Thundercloud, free Unleash and others. Take Divine Seal, it could be changed to a 25% chance of any given heal being increased by 30%, or to a flat 7.5% healing buff. Either would be simpler for players to handle at the cost of finer control of battle. With every change of this sort, the ebb and flow of battle is mellowed, making gameplay more consistent but less involved. (and I'm not going to get into the pros and cons in an aside in a post I'm making at 3am)