You could have a toggle to use 'custom UI' or default 'shared UI' in each Gear Set, just like now each Gear Set remembers if you want you head gear and weapon shown or not. That's not difficult to code.
Just add a menu command to the Gear Set menu (Equip set/Display set/Preview/etc) to copy UI settings from one Gear Set to another.
Separate skill bars for sheated/unsheated weapons are available only for gamepad. You shouldn't be using gamepad for anything besides fishing/gathering anyway. Also, how would it know which skillbar version you want to use on the Wolves Den Pier? Your idea is doable, but I would like to have more control over what skill bars I use with each Gear Set. I'm not entirely against your idea in this point, it looks fine.
FFXIV is developed primarily on PC and then ported into consoles with some functions castrated out. I don't mind PS3 and PS4 missing some quality of life features as they are inferior systems already in many areas - you shouldn't use console for anything beyond crafting/gathering and simple solo play. So if developers can't figure out how to store character data on a console system, they should just omit the feature from that system. If you want full experience, you need PC already anyway.
Thanks for that, that's very disappointing underestimation from developer side.
Also, at launch developers promised us addon support six months after game release. And any features brought in through addons found to be popular/helpful would be hardcoded into the game itself for console users to take benefit. This has not been delivered yet, but if save data on consoles is so limited, I'm worried the developers will choose to hold back game feature development and ultimately do a great harm to the game. Just like FFXI has not yet reveived HD remake and is missing a great deal of features due to 'PS2 limitations'.