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).
