XIV has lots of features that XI could use, just as XI has lots of features XIV could use. And I'm not saying this to make the games more similar, these are simple features that wouldn't change the gameplay. Many were already mentioned..

1) Linkshell embles/shield crests
2) Retainers/bazaar mules
3) Better crafting system
4) More teleport points (although admittedly moving around is a lot easier on XI by now)
5) Show status effects of party members
6) Show remaining time on own effects
7) Multiple linkshells equipped
8) Better chatlog filtering/organizing, customizable tabs, different log windows
9) Minimap on the screen
10) Customizable HUD
11) Using the numpad to input numbers
12) Built-in IME support
13) No POL, better/faster login and updates

Just a few, I'm sure there's more. Again, not saying there aren't things XIV could use, the list is easily twice as long. However, XIV is a very new game compared to XI. Some of these features have been suggested for XI for ages (literally) and are still not implemented.