Fix the hitbox issue with hunting on auto-move-to-target for good. There have been improvements, but adjusting a screw here and there did not remove the fundamental problem.
Fix UI annoyances which have been reported over and over for years: Storage to open next to inventory, save map status, save waypoints. Make items sortable within their inventory compartment, automatically group by set (armour and clothes; materials by category as in the auction house). Move treasures in inventory to mined resources, since they are mined and the materials tab is really overfull.
The client does not handle network errors gracefully. There is no good reason why the whole heavyweight client is forced to shut down upon a timeout, even if the gap is too long and a re-login necessary. It would save time and money especially in situations where you lost connection right in the middle of hunting and scramble to get back while your mob regenerates. Kick your network guy out of the LAN and place him in a mountain cabin with only a 3G stick for a week.
Unshrink ancient pets (this was a cardinal sin). Restore the old Minopolis. Restore the old Jason Centre. Stop laying waste to every nice place on Calypso.
You could put Hiryuu spawns on the rooftops of the four huge buildings at Fort Ithaca (fun to fly up there and fall off again...), and around the sky platforms at Athena Spaceport. This mob is still a pain to gather in numbers for the mission.
Athena Spaceport - it is highly counterintuitive that vehicles are banned from it. Make it viable using the sky platforms to launch into space. This will be popular because it saves fuel to start from higher elevation. Put televators near the main tp, because the way up there is too long when doing it often. The whole place is spectacularly pretty and sadly underused.
Improve the availability of Dianthus, Pyrite and Dunkel. (I am not subscribing to any theory about hoarding, caps, or whatever. Only MA knows, they made it so. I'm asking to revise the decision.)
Do something to make weapon economy enhancers usable, at least so that they don't worsen economy. Their markup is prohibitive and a turn-off to players who find this out the hard way. If they just serve to stretch durability, this would be useful in some cases. Maybe renaming them to Weapon Durability Enhancer would help people getting off the wrong idea, along with improved resource availability. Unlimited blueprints would make sense then, too.
Add a Divine Drake to Next Island, offering players a choice to exercise preference when doing the mission for their DI chip (5 out of 6), and thereby also making a statement that Next Island is to be preserved. (If we want to take it further out, there could be a divine space mob also, which makes it 5 out of 7; or even a potential expansion of the DI mission to two stronger chips with even higher intervention chance, obtainable after the relevant stages for Imp/Mod Resto for which you need to do 6 and all 7, respectively.)
Offer the possibility to return an Adjusted or Improved Restoration Chip to Dread Castamir for continuing the mission to a higher chip. This way some selling pressure is taken away, at least from those who wish to upgrade. Market prices have already fallen below cost to make a new one, this had to be anticipated.
Scrap the non-refundable auction fee. Take your 5% of the markup upon a successful sale, this is still above shopping tax. Or maybe take 10% up to the first 1 ped to compensate for the lost pedestal and the load when this change leads to increased number of listings. As it is, market stats are deceiving as they don't give a clue about the number of unsuccessful attempts. Every newbie learning the hard way from trying to sell a Rubio, Lancehead or freshly crafted Jester feels betrayed and pushed a little closer to quitting.
Most of the above points have been sent in via support over the years. Thank you for your kind consideration.