I hope my improvement suggestions will be heard by FF14 Development Team:

1. Ability to reorganize the retainers list:
I want to be able to reorganize the order of my retainers in the list that I appears before I summon the retainers. The game currently has no option for doing that. Right now I am emotionally refraining to hire more retainers with the class I want because I would not like the order of retainers that would appear.

2. Changing retainer class (Combat)
I think we should be able to change the combat class of a retainer without resetting its level to 0. I understand for gathering classes, because the items that they gather are different. But the items we gather for combat classes are the SAME. I think we should have freedom to explore combat classes and not be tied down by retainers because have to reset the level of the combat retainer to 1.
For example, I have WHM 50 and Retainer is WHM 50. Then I level up WAR to 60, then if we want to change the retainer to WAR, we should not start all the way from lvl 1. If you are afraid that when we change the retainer back to WHM and it will be at 60, then you can just set the retainer lvl to our class lvl, for example, change the retainer level back to 50 if my WHM is at 50.