I think in general the idea here is to create a game in the spirit of the originals rather than in the exact form.
If the developers back then had a different engine and different technical capeabilities, theyd have made different games. And you can see this from later DnD games like Neverwinter Nights or ToEE.
If they were to make one today, i figure it would be closer to Dragons Dogma than any infinity engine game.
Regardless, i think the issue you are discribing mostly comes from the system itself. DnD is a very abstract system and it is so for a reason:
Its a PnP game and simulationism can be a pain in the arse, if youve ever played The Dark Eye you know what i mean.
5E is a notoriously easy to run and low depth version of DnD, the reason for this is that 3.5, the edition 5E is based on was very cumbersome to run due to beeing very bloated with material.
2E which baldurs gate (besides the dark alliance ones) is based on is an older, more archaic version that had its focus very clearly on the dungoen crawling aspect, something the game took a step away from in third edition.
Introductions aside, DnD is an abstract game because that makes it easy and fast to run, however, one of the strengths of a PC game is that you dont have to consider ease of running. Thats probably why NWN with its port of the third edition ruleset became very popular. Also why people bemoan that there never has been a fourth edition video game.
Which kind of leads us to enviroment interactions. To someone who doesnt play DnD, this most likeley seems to be an issue. As DnD doesnt have enviroment interactions in the way Original Sin does.
This however is completley untrue, ill give you an example from a very early point in the campaign im DMing right now.
AS you might now, Dragonborn are a core race since 4th edition and a friend of mine played a Dragonborn with the Thunder breath ability.
In one of the first couple of enocunters, my party was fighting a Tribe of Kobolds, while they were engaged with Kobold skirmishers at a riverbank, kobold reinforcements were wading through the shallow water, so my player decided that she would use her breath attack on the kobolds in the water.
When i was about to tell her she hit two Kobolds she told me she expects to be able to hit all of them, as they are all partly submerged in water and sureley her electric dragons breath would fry the lot of them.
This lead me to homebrewing the effect of this interaction on the spot.
So its not that DnD doesnt HAVE these thigns, its that it doesnt have rules for them because that leads to some very cumbersome gameplay. Also editions like 4E are centered around balanced gameplay rather than simulationism.
What Sven said when he talked about "Systems" is that he wants to put systems into place that simulate a Dungoen Master. An arbitrator of what you can and cannot do. Naturally this can extend beyodn the rules, anyone that ever DMed will tell you that you probably cant make it to session 2 in any campaign without having to houserule one thing or another.
As for RTWP: Im gonna make myself realy unpopular right now: but RTWP is a terrible system that only exists due to the limitations of their time. It was an attempt to emulate the DnD ruleset and thats it. It snot some sort of holy grail. It leads to terrible combat and repetetive encounter design in which only a couple of encounters will actually be thought about while most of them will be "right click toe goblins".
From Svens combat, i think we wont get either RTWP or Turn based but a completley different system alltogether. my money is on something like Divinity 2 or maybe Dragons Dogma.
