I realize most of these have been suggested before, but I think we should continue to advocate for certain feautures to be added for convenience:

-Expand trade slots to have a 5-6 item maximum, since most endgame sets are considered 5/6 pieces, instead of the original 3-4pc sets that the game originally had. Possibly reduces the chaces of scamming/need of a middle man
-In game mail system, where you are able to send messages, items, and gold(?) to offline players.
-Stash Categories and Search Bar, similar to inventory and CS
-Online player statistics, the game used to display how many people were online at a given time, it would be nice to have that feature again
-Option to reroll stats while in a pvp game

Feel free to add additional ideas