Definitely agree about the whole party interacting. I feel like that sort of thing dropped off a cliff after Dragon Age: Origins. (I recall KotOR and Baldur's Gate 2 being really good at it).
That is a simple thing that I'd love to see more of in PoE2. More inter-party banter! (I honestly don't remember if PoE1 had any of this...)
This is obviously personal preference, but I feel like "character development" as a whole is somewhat overrated in media. Or not really overrated maybe, but too much importance is placed on it. I've known people in real life who haven't really changed much in years. Most games take place over a few weeks or months, and yet there seems to be this implicit expectation that everyone involved will change fundamentally. More than that, often people have the additional conceit that not only will they change, their PC is the impetus of that change and directly influences its direction.
I think that's OK if it's for one or two characters, but as a general pattern it strikes me as very silly.
It's not even about choice and consequence or anything, but NPCs/party members acting as characters rather than props. Like, too many games treat party members like extensions of the player to be done with as the player pleases, which is a gross underappreciation of their potential as characters and agents in their own world; in the worst cases, it's like their existence ends the moment they join the player. It would make for much more interesting games and worlds if they had more consistency.
Oddly, of all games Dragon Age: Origins handled NPC agency excellently. Party members had personality on top of agency--they could directly decide their own fate. So, if the player did something they vehemently opposed, party members could leave or even attack the player. It doesn't have much scope beyond that (except in vague epilogues) but it is still so much more than most party members ever get.
And as far as altering personalities and stuff, yeah, the timeline is crunched down a lot for games, but when you're deciding the fate of entire factions, if not the world (in most games) it makes a lot of sense for them to be heavily affected. Not to mention all of the experience, skill, loot, and power they accumulate by virtue of being in proximity to the player.
But, yeah. Romances in RPGs are often handled weird though, I think. I don't know what it would take to really do well Probably scaling it back from "romance" into something with more gradients, like rivalry/friendship/romance depending on the character in question. (DA2 tried this but failed hard.) But then it balloons the writing scale, because everyone will have different inclinations for how to treat the potential relationship candidates.
I don't know that PoE2 really has the scope for something like romance (or whatever) to be successful. PoE1, IIRC, was pretty spartan with character interactions, so it'd be a big change. I'm curious if one of their updates will mention anything like this.