Honestly, exploration is one of the weakest points for me in this game. I would keep EVERYTHING as is, including turn-based combat, but place our characters in a large open-world with hidden dungeons that require solving puzzles or perception checks. I honestly think this would be in line with what people imagine the world around them to be in tabletop.
You could also divide the map in smaller areas between which you "travel". Exploration in BG1 was exactly what you describe without the things that may be boring in open world (filler content in exemple).
I like the seamless nature of the current world and open worlds though. Having a bunch of transitions is a little choppy to me, but I understand why someone might like that. I wouldn't mind a bigger world that is still seamless which has a bit of somewhat less deep content to fill it. A bandit camp here, an village taken over by the Absolute Cult there. I'm reminded of the Ancestral Tombs in Morrowind, which were scattered all over the map but were essentially one to two room places to raid for a bit of loot.
I know I can't be the only one to feel something strange when a vast world with diverse geography opens up before you and you can go anywhere you want. I think that's immersive as fuck. Just walk in a direction, and there's world, and stuff, and if you keep walking, more world, more stuff. The principle here is a sort of freedom of movement and exploration at a massive scale. Again, I'd keep everything else, but I'd revamp exploration and traversal.
