One Joomla's feature I would love to see in eZ Publish is the way you can update the priorities. This could be applied to both priorities for subitems or for attributes in content class edition page...

With an example from editing a content class.
Currently, if you happen to have added 10 fields and then realize that you need a new one and want it to be priority 3 you have to change the priority value of all fields starting from the #3 which is annoying. If you just change the new field's priority value from 11 to 3 and apply the changes, eZ Publish will just shout:
"attribute 'new_attributeXX': (427) duplicate attribute placement "

What Joomla does is it will internally re-order the whole thing and where there are duplicate priority values it will just alpha sort the duplicates ones and then readjust the priority values of all fields starting from the duplicated one.

Example:
1 - Title - prio 1
2 - Intro - prio 2
3 - Body - prio 3
4 - Author - prio 4
5 - Link - prio 5
6 - Image - prio 6
7 - Document - prio 7
8 - GMap - prio 8
9 - Published Date - prio 9
10 - Expire DAte - prio 10
11 - New Attribute 11 - prio 11

Setting field #11 to priority 4 would internally gives:
1 - Title - prio 1
2 - Intro - prio 2
3 - Body - prio 3
4 - Author - prio 4
5 - New Attribute 11 - prio 4 ****
6 - Link - prio 5
7 - Image - prio 6
8 - Document - prio 7
9 - GMap - prio 8
10 - Published Date - prio 9
11 - Expire DAte - prio 10

Chich then should change to:
1 - Title - prio 1
2 - Intro - prio 2
3 - Body - prio 3
4 - Author - prio 4
5 - New Attribute 11 - prio 5 ****
6 - Link - prio 6
7 - Image - prio 7
8 - Document - prio 8
9 - GMap - prio 9
10 - Published Date - prio 10
11 - Expire DAte - prio 11