while it's not necessarily experimental content, as something new and innovative i feel like expanding on the GC via FC's would be cool and a good way to do it without trying to figure out content going forward with squads and other GC specific ish stuff.
add in FC alliances in game wise if players all have squads (lore wise) and you have multiple fc's while you may not be the actual leader of a FC or the alliance the game could just say you are as a way to not worry about specifics and add content for fc's/ fc alliances it does have to require many players or even players in the same said alliance/fc this way people can participate without having to worry about finding a fitting specific group which can be challenging as its easier to not get along with someone than it is to.
with the addition they increase the obtainable GC rank 3 to the high commander as a start to see how well liked it is, and add FC content attached to GC be it worked through individual players GC/FC's/or Alliances, course alliance could not be attached to a specific at all since it would be weird for each FC to be attached to a GC then the whole alliance attached to completely different one but thats just a minor point.
this is just an idea to have a way to add content to FC like they tried with diadem but it failed and a few of the reasons was at first it required just your FC and a FC airship which wasn't good the second is the content was never great and rewards mediocre so i believe if we start out with a completely open idea of players can just participate when they want and even with friends of other fc's and no forced attached your specific fc/group it will have the chance of becoming popular.
i know the game could use some more community based content and at least a start/reason to have a FC besides buffs and a FC chat would help.
edit some actual content idea's for FC/GC content.
some basics that isnt super new but would be nice.
FC/alliance quests be it daily/weekly/monthly just something to hop on and do nothing super needy but something to be added that would feel like something a FC can work towards like dungeons run/leves completed/turn in done ect. nothing out of the way or maybe something alittle out of the way if someone more creative can think of something cool.
also maybe fc specific maps to get something needed to upgrade alliances once again nothing super special maybe put some rewards behind these that can only be obtained through this once again nothing crazy but something to get people to try it.
fc/alliance hunts waaay in the past SE wanted to do something with fc primal hunting/summoning but instead of that we can do just fc hunts they could be done some how through it with an item or a quest that can be done some how. could always just attach it to normal hunts but that sounds like it would only cause more problems if its done on anything higher than B rank for obvious reasons.
something dumb but could always take one of the pvp maps and rework it to have an alliance pvp zone it could work like frontlines but instead of queing for it, two fc's could iniate a que/match that you would just have pre made groups already done that could que right in.
this is just some thought with like 5 minutes of pre thought. but i say some more content for FC's would be nice i guess technically they wouldnt need to attach any of it to GC but i feel making a lore reason to attach adventurers/ adventurer FC's to GC would be a plus.
lastly the add a GC to all the major area's ishgard/kugane/thavnair/sharlyan/tural. (this one is my crazy too much work not worth doing at all suggestion but i would like) they removed any and all GC pvp requirments so it would hurt pvp and they could always add them into pvp later that way people could have more choices in GC.