Some were already suggested but here is a list of some things I would love being impelemented:
-boon- and condition-bar being movable
-being able to dye at least backpieces
-character-specific keybinds
-better search options at the TP, like filtering for light, medium and heavy armour, price ranges and stat-combinations
-being able to go into queue for all WvW-maps at the same time when all 4 are full. (random, 1st free place)
-additional bar for consumable items, minis, etc.
I guess I’ve forgotten something but I’ll add it later if I hit on it again.