Here's my list from about five years ago. Some of these things have been fixed.
1. Start mage merchants with more than 20 of each reagent. How about 100, which is a day's adventuring for ONE person?
2. Double right click to remove spell icons from the playing area. As it is now, it is too easy to "lose" an icon when you want to run, especially when playing 640x480 full screen/full screen.
3. The mage vendors in Luna "blink" very often. This makes buying from them very difficult -- in the middle of a sale, they "blink" and the buying menu disappears. Just lock them down.
4. Make small blackrock pieces stackable. Do the same for fire ant goo, slug slime, fish food, tasty treats.
5. The "mini-boss" of an Abyss mini-spawn should always have at least one of the Essence for his area.
6. Get rid of monsters looting player corpses. That's not fun at all -- especially in a spawn area, where a monster's body decays so quickly a player is unlikely to recover his items. Or perhaps they could be limited to looting only food and gold.
7. Useful items need to be made available. It sucks to be a new player, finding out that useful things like the lucky Conjurer's Garb or Conjurer's Trinket can't be had at any price.
8. Enemy Of One does not appear to add a damage bonus to someone wielding a slayer weapon. Please fix.
9. Allow characters to instantly log out in their homes or at an inn. You're half a world away from that combat you just escaped from.
10. When you buy something, put it in the same spot in the backpack all the time. This will save time afterwards looking for it, especially for things that are the same color as the bottom of the backpack. Do the same for trades.
11. Allow grandmaster or above smiths, tailors, and tinkers to "repair without weakening" (it used to be this way).
12. Get rid of "cannot be repaired" and "brittle" and "cursed" properties. Those aren't fun. Someone on the Dev Team doesn't play the game at all and is himself a wet blanket.
13. Allow Fey Slayer property to be imbued.
14. Consistently use Elizabethan English ("thees" and "thous") and fix all existing text
15. Have gargoyles use infinitive verbs and fix all existing text
16. On the classic client, save the state of the menu being closed
17. Boots of rapid quicksand walking
18. Arcane talons for gargoyles
19. Ability to alter aprons back and forth between gargoyle and human (sheesh, reality would be just tying the strings a little tighter for humans; who can't do that?)
20. Ability to alter elf clothing for human. Alternatively, have some human-only craftable armor that's equivalent to the elf darkwood set.
21. Ability to use interior decorator to "turn" weapons that have two different facing graphics
22. The "Guilty" quest. Make a story about how or why Gregorio can't be harmed, and have the Lady of Skara Brae give an item which overcomes it.
23. Have Incognito toggle
24. When you kill an NPC under Trammel you get a "You cannot loot that corpse" message. Just let me loot it.
25. Use the same (Necromancy) wraith form graphic for both sexes. As it is now, males have a tremendous advantage in PvP -- hard to see, hard to target.
26. Mouseover of a vendor backpack should show the number of items. As it is now, there's no quick way to tell how many items a vendor has.
27. Shared storage that can be accessed by all characters on an account regardless of which shard
28. Quest for human/elf->gargoyle and gargoyle->human/elf
29. Allow pets to be resurrected by a town vet without the "That creature's spirit lacks cohesion" delay
30. Gloves that will allow humans and elves to use throwing weapons (make them good gloves equivalent to Stormgrip)
31. Allow Honoring an opponent without doing the path find. The path find is defective. You never find a path to something that is flying, even if it's right next to you and you can hit it with a melee weapon.
32. Upon login, write the date, time, and character name into the journal, e.g. Woke up: David 10-March-2012 5:54 a.m.
33. Make it easier to change the journal file used
34. We'd like a gazer slayer weapon property
35. Give a message only when Perfection changes. Seeing "you have achieved perfection" messages each time you swing a weapon isn't useful. Better yet, make an icon for the "buff box" that graphically shows your amount of perfection.
36. A set of talon armor for gargoyles that has the same damage absorbing properties as swamp dragon armor for humans and elves
37. Wider flying areas for gargoyles. Why can birds fly over water and gargoyles can't?
38. When you recall across a server boundary, the contents of the backpack get z-ordered the opposite way. Stop doing that. It's annoying.
39. On the classic client, have the Options save to hard drive when you click OKAY on the dialog box. The way it is now, it doesn't get saved if there's a client crash later, or if you lose connection.
40. Double the amount of arrows a quiver can carry, to 1000.
41. Make quests for Spirituality and Humility virtues, and make an alternate path for Justice that does not require PvP.
42. An equivalent of mining gloves for gargoyles
43. Allow recalling out of Heartwood
44. Allow checks greater than 1 million. Have checks combine by dropping one atop another inside a bank box.
45. Have additional acid popper quests that can be done more than once.
46. Reduce skree to two control slots, or beef up their melee attack damage, or allow them to learn higher level mysticism spells. As it is now, a nightmare is a better pet.
47. Have Animal Lore display a pet's mysticism skill where relevant
48. Reduce bonding time for pets. Perhaps using tasty treats or deliciously tasty treats would reduce the time.
49. Some monsters when carved produce "Cut of Raw Ribs" that does not stack. Fix that to be the stackable kind, then ask yourself, "why are there objects that look and are tagged identically, yet some stack and some don't?"
50. Allow adding charges to arcane clothing without first using them up completely
51. Allow a vendor to hold more items
52. Allow taming of cu sidhes by non-elves, or introduce an equivalent self-healing ridable that is human-only
53. Have damage done by pet appear in a different color than damage done to pet. How about orange?
54. Bring back the Ultima Online music (mp3-ize the old MIDI files, with the good sound)
55. Provide a way of changing the description and price of an item that's on a vendor without removing it (context menu)
56. Take the 500 limit off seed boxes.
57. Allow honoring of a monster that has cast bless on itself (they get the "too damaged" thing)
58. Get rid of the "ephemeral" property. Just let us buy the good stuff with our void pool points. See #12. Someone on the dev team really doesn't want us to use or keep good things.
59. Reset ALL "about a day" timers at server up
60. For escort quests, remove the "must wait five minutes." Instead, have doing more than five in the 24 hour period get less gold. Hey, they know transportation is plentiful.
61. Allow a lone spellweaver to get a focus.
62. Change a spellweaver's focus only for the better. Some chucklehead is always doing the spell after someone's stepped off the arcane circle.
63. Have a bulk order book count as one item regardless of how many deeds are in it
64. Have the classic client "remember" your password (fill in the field) every time except when you first start a session. You shouldn't have to retype it just to change characters.