My thoughts in brief:
(1) A team of NPC companions shall be encouraged. Each NPC companions has his/her unique (yet multiple) paths of development, based on the decisions made for his/her personal stories. Each of them have their storyline like the watcher, which can also compensate their inflexible innate attributes. Their FATE is what makes them real and vivid.
(2) A team of fewer companions shall be encouraged. Four for Hard mode, three for POTD, for example. Fewer players enable a higher degree of micromanagement. It makes positioning and strategy critical.
(3) A simpler spell systems for casters. For me, the more complicate the spells, the fewer of them would be used. Complicate combos or strategies can actually be generated from a simple system.
(4) One-or-zero boss fights: If my beginning shots landed successfully, the big bosses all die in a few seconds. If not, the fight may take up 10 minutes or even 20, and there remains no hope of overturning the miserable situation. It's interesting to learn the tricks from try and errors but shouldn't such learning curve rely more on playing skills rather than on pure probability?
(5) Food/Traps: How could one take 6 dishes of food, plus 1 drink, plus 2 drugs and still could jump up and down... It's also crazy to do so for 6 members. Besides, why should they be placed in the quick item slots if they cannot be used in combat? Food should be like 3 or 4 meals a day. Otherwise, it is medicine or drug.
(6) Camping/Caravan/Stash: The adventurers should be able to travel with horses and wagons to where they have already explored and cleared the paths. Two or 3 days' travelling across the map shall not increase their "fatigue". They should always have access to their wagon and stash as long as in a safe area. However, moving into a hostile dungeon or closed maze shall disable them from accessing their caravan/stash, which is parked "outside".
It's been awhile I haven't played an RPG game as impressive as POE. I couldn't believe that I've spent 400 hours on this game already. I found out probably most of the time "spent" was that I stared at the static character sheet or inventory panel, thinking, moving things, fine-tuning, looking everywhere for a right spell, a right trap, a right scroll, a right item, etc etc.... or perhaps fallen deep in the thought of how much I adore my char.... just kidding, well, the fact is I realised I focused so much on defeating the enemies that I totally neglected the "stories".
As a matter of fact, I haven't even completed ¾ of the second play-through. I did enjoy overcoming all the difficult encounters with my TRIO, but I also lost my motive to continue once I defeated the mage in the White March Part I, leaving Endless Path and ACT 3 untouched. By the way, my TRIO is Chanter, Cipher and Rogue. Casters seem to make my micromanagement over complicated and over time consuming.
Another fact is that I tried using the NPC companions but found myself not hooked. They are humorous or hilarious from time to time but well, at the end it makes no difference, perhaps. Decipher the complicity of the skill and combat mechanics seems the only thing in my mind. All decisions made alter nothing but the rewards the player's character receives.
It's not that I dislike this game at all. I like it very much. I just don't like myself lose the interest in the stories and roles.