Yeah i believe they were going for a more Guild Wars 2 approach where you only have 10 slots to put skills/feats in and according to which abilities/skills you slot your playstyle changes.
Costumable UI to move around chat screens, minimap etc would be nice. It gives you a personal touch. Same for keybinding.
I'm not that fond of mods/plugins but that's a personal opinion. If they go that way they'll probably be available for everyone so you have a choice if you want to use them or not.