The Quality of Life update I would be most interested in seeing is a way to sort your mods by primary and secondary stats in addition to the set type. It would take all the headache out of it for me.
A slider for purchasing data packs would be nice.
As would a multi sim button for fleet.
Improved guild chat would be excellent. Especially if it allowed hyperlinks.
Detailed raid history would be excellent too. Being able to look at individual attempt stats instead of just absolute damage totals could lead to a lot more people getting the hang of raiding a lot faster.
Picking your opponent in both PvP brackets would be a nice addition as well.
It would be nice to see a tweaking of the algorithms that control the random stores so that characters that are already 7 star are less likely to appear than ones that aren't. but that's probably asking too much.