A massive, in-depth open world COULD improve exploration. But it shouldn't come at the cost of everything Larian has been building in their age of the CRPG renaissance. There's an indie game whose name is escaping me that is in development and has open world exploration, but switches to turn-based when combat begins. I think that could work here. It makes me wonder, though, why I am so fond of vast open worlds and free exploration. Maybe I just have fond memories of Bethesda and Obsidian games. But I do think there is something really cool about exploring a seemingly vast landscape dense with mystery and hidden features at your own leisure. At the same time, I think it would involve sacrificing everything that made DOS, DOS2, and BG3 what they are now. I know I hate the theme park effect and that a true open world could help with it. I don't think any of that qualifies as making the game more normal or legitimate though. In light of the roles of spells and abilities influencing how we traverse the world, I would much prefer something Morrowind-like in exploration rather than Skyrim-like.
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.