I just finished my first play through and I have a few insights I can add to the list:
1. Too often I would finish an encounter with one or two characters stabilized after 3 successful death saves and no way to heal them. This could be fixed by allowing other characters to use a healing potion on those downed companions. It should also be noted that abilities and spells that grant temporary hit points, (Aid and Rally come to mind), should also allow the downed character to stand up.
2. I know many people are asking to be able to choose the character to resolve conversations to benefit from better skill rolls and it's a great idea. To deepen this, it would be nice if you had two characters that shared the same skill proficiency be able to take the "Help" action to gain advantage on the skill roll. Conversely, you could have a good cop/bad cop situation where characters use opposite skill checks, Intimidation/deception/persuasion, to succeed on the check.
3. Selling items for the best price possible is too much of a hassle. I would spend 20-30 minutes of my time making sure Shadowheart or Wyll had all the items before speaking with the trader to get the best trade or most amount of gold. I would suggest an "Add all Wares" button that would pull from all characters/your camp stash to make this process less time consuming. It would also be nice to have a hotkey to mark items as a ware to expedite the process.
4. The single minded focus enemies have on characters, especially when they're rolling death saves. It's a real pain to have to constantly carry resurrection scrolls or go back to camp in order to revive a fallen character. It took me out of the immersion of the game to spend extra time and money constantly having to bring someone back. An easy fix for this would be to have enemies redirect focus to other characters or to throw in an extra ability for the "tank" classes which allows them to pull aggro.
5. The last bit is on the jump and shove abilities. The main issue I have with Jump is the ground stomp effect that deals damage and pushes targets that larger creatures get. Shoving creatures should take the place of an attack to either make the target prone or to shove them 5 ft or outside the AoO range. I feel it's being used too liberally as an additional way to inflict damage. It would be nice if a dex save was put into effect to stop a shoved character from being pushed off higher ground.