I think the divinity engine and combat would be perfect for bg3. Most features in 5ed simply rely on turns, such as Assassinate and gloom stalker's extra attack.
Be more honest. It's not perfect for BG3, it's perfect for saving money. Which is what you want, right? You want to recycling the same tools you used for your earlier turn based games and save some money that way.
Changing the franchise to turn-based is frankly a massive disrespect to the precious two games. Let's not pretend the previous games didn't have concepts of turns and rounds. Giving someone an extra attack per round, or applying some special conditions to the 1st round was never an issue in the previous games.