A selection of ideas

[MeiraStarborne]

-A glamour plate per class, perhaps with a couple extra for swim/civilian/nightwear (could even charge for them in the cash shop, I know a few people who'd pay)

I'd love for more glam plates. Yes, I would pay extra each month even for this feature. I already pay for extra retainers, I could afford another dollar or two a month for glam plates — and some additional glam dresser space while we're at it!! (Or better yet a system like WoW has where once you've acquired an item once, it would be available for glam, eliminating the need to store the actual item in a dresser at all.)

-More control over what your retainers look for for you, not necessarily a guarantee but an increase chance of getting -item type here- possibly also including from -this level bracket-

This already exists. When you send your retainer out on a venture, you can specify what you want them to bring back. Miners can bring you anything you've previously mined yourself. Same with Botanists and Fishers. Combat class retainers can be sent out for any meat or leather or other animal "drop" item. It's a 100% success rate, and the interface tells you exactly how many of that item they will fetch.

-Level skips for crafters/gatherers, including mastery (another one I'd personally pay for...)

Going to disagree with this suggestion. The only reason combat class level skips exist at all is because SE added story progression skips. They only reason they added story skips was to encourage new players to subscribe who thought it too daunting and time consuming to play through the entire content. The wanted to attract more subscribers and know that after the base game and now 3 expansions that many potential new players feel it's too late to start FFXIV because they'll never catch up and always be behind. As the product description says for the progression skip on the online shop "New players looking to jump straight into Shadowbringers or enjoy adventures with friends already playing the game can now catch up in the blink of an eye!" You would need 1 combat job level skip to accompany that story skip to actually join your friends in Shadowbringers content.

Crafter and gathers are not required to play the game. While people can (and do) skip other combat classes just to avoid actually putting in the time to level them themselves, it is not exactly the intent for why SE added level skips to the shop. So, adding skips for supplemental content isn't likely to happen, and in my opinion, shouldn't. As stated, leveling gathers and crafters has been greatly expedited by the addition of the Ishgard Restoration and Diadem. Additionally, Grand Company leve turn-ins grant huge experience for crafters and gatherers. So, yeah... Lots of ways to level those jobs quickly if it's something you'd like to do.