I know you've updated Potions and Food, but here we go:
Guildhests - just think of them as another bit of content that people can do where they get a little explanation with what they are doing. It exposes them to mechanics that are seen elsewhere in the game. They're also quick and offer up a once per class exp and gil bonus - I do them just for that.
Potions - as a MCH with no native or cross class self healing, Potions are my only choice. They do need bumping in effectiveness, and we know that this will be happening from the recent Live Letter. NQs have a 120s cooldown (HQ is 108s). X-Potions are about as good as having Second Wind (same recast, too) for me. Potions that increase stats are actually very good - +105 of your main stat is a huge bonus. Or are you telling me that increasing your stats is completely unnecessary and on one would ever upgrade their gear/weapons or use damage buffs like Blood for Blood? They may have a long cooldown of 5m and only last 15s, but if used like any other cooldown (especially when used as part of a burst) they are incredibly powerful. World Firsts will make use of these at every chance.
Food - is a 30m+ buff to your stats. Accuracy food is especially very useful for times where your gearset is unable to meet the requirements (eg an upgrade would cost you accuracy but also produces better damage/survival/healing etc).
Chocobo Fighting - Very useful when solo, at least for me. Like with potions, I don't have means of healing myself so I rely on my bird to do that for me.
Hunting Log - This is a viable source of exp for those classes. Why would you remove a means of getting exp for a class you wanted to level up?
Sightseeing Logs - With HW, this is also something that gives exp. As I was flying around the map doing my sidequests, I kept an eye out for these. Being award 18k exp for simply using my eyes is great. In the ARR zones, these were added simply as something to do. Some players find figuring those things out to be fun. Why do you want to remove someone's source of fun? That's a pretty crap thing to want to do/say : "I don't find it fun so you are not allowed to either?"
City to City Airships - I'm going to go out on a limb and say that I don't think these task the servers enough to warrant even considering removal. Some people do like to use them rather than continuously spend their gil - teleports do add up in cost. Plus, I'd expect a few dedicated RPer types enjoy using these. Again, why would you request to remove someone's potential source of fun and interaction with the game?
Treasure Chests - Please keep these. My FC runs a weekly treasure hunt event and people find it very fun to do because they get to play together. We also use this as a means of fund-raising for the FC. It funded our large house, and is currently funding our airship projects. Again, just because you don't like or use it does not mean it should be removed. Only if 0 players ever touch the content, should they do that.
Linkshells - Maybe you don't need any of these, but I have 7 that I use very regularly. Not always do I want to talk about things in FC chat - and not everyone wants to read the stuff I could put in FC chat. They also let you stay in touch with players from other FCs.
Irrelevant Quest Lines - And again, just because you don't want to do it doesn't mean no one does. I do this content for the hell of it. I don't need to be rewarded with usable loot to do content.