I know IWD2:EE has not been confirmed (neither has PST:EE), but the following are my thoughts on what the devs should change and/or improve in the EE.
The first thing is that although some have asked for it, I would not switch to 2E rules. I consider the 3E rules to be the best part of the game.
Obviously they would need to port it to the new engine and redo the UI in the new standard. This would be quite a lot of work on its own of course. Just have the game able to run fullscreen in Windows 10 and look good would be great, for instance.
Next, I'd implement a few more high level spells. High level spell choices, especially for druids and clerics, are extremely lacking. So I'd implement a few more level 8 and 9 spells. They don't necessarily need to be from Baldurs Gate 2 - for instance, I'm not sure whether I'd implement Timestop.
I'd also unify cleric spells and cleric domain spells. Clerics currently have two separate pools of spells - Domain and Cleric. Cleric spells are the regular spells that all clerics get, Domain spells are specific to an order or domain (such as Oghma, Lathander etc). However, the problem with Domain spells is that you only get one slot. This is different to how NWN for example works. So I'd make it so that instead of two separate pools of spells, Clerics have a single pool, but still differentiated between orders. For instance, only Oghma could learn Identify as a level 1 spell, but now they would have more than one copy.
I'd revamp the following underused classes - Fighter, Ranger and Barbarian. Fighter unfortunately is the most vanilla class and nobody bothers taking more than 4 levels of fighters. I'd implement additional feats to make it worth your while to take more levels of fighter. Maybe feats that increase melee damage?
For ranger, I'd implement more two weapon fighting feats.
A lot of people don't have problems with the barbarian class, so my only change would be to remove the damage resistance (which is so low as to be useless anyway) and replace it with adding your constitution modifier to your AC if you are unarmored (but allowing a shield). This is ripped from 5th edition. I think it would be really cool because it allows for unarmored barbarians that don't totally suck. This would mean that the AC penalty of rage would become null and void though. Not sure how to balance that, an option would be to remove the AC penalty and then change the saving throw bonus to a saving throw penalty.
I'd change the difficulty balance of the first part of the game up until the end of the Horde Fortress. Its too hard and tedious. I'd probably remove those war drums, or else, make it so that the war drums only work once. In other words, beating on the drum only summons two Worg riders and thats it. No endless supply. I'd remove Trugnuk's ability to cast call lightning too. As for the battle of the Shaengarne, I'd just remove one or two of those boars and maybe replace them with Orcs. The boars and the Malarite priests together are a little too difficult for low level parties.
I'd change Battle Square to be more like the Black Pits. Instead of one on one combat, it should have progressively tougher group battles. The golem could teleport you to an arena where you battle a group of enemies. Only one group battle needed to win the rank, so ten battles in total.
I'd investigate increasing the difficulty of some areas later in the game. By the time you get access to high level spells, some of the later areas can be a cakewalk.
And the last thing I'd do is revamp that Challenge Rating system that everybody hates. I don't know exactly what I'd replace it with, but I'd want to remove the incentive to level squat. Purely psychologically, when you get one level and your experience from killing an Ice Golem Champion drops from 5400 to 3600, you kinda think Huh? You feel shortchanged. I don't know what the answer is, I just think they can do better than the CR system.
What do you guys think? What would be in your wish list?