+1 to going back to the original 5e stat blocks for monsters. WOTC has already playtested all of these monsters for appropriate challenge ratings so why do extra work by adding levels and attacks and then rebalancing? D&D is already fun, no need to mess with the formula this much.
I get people who want Divinity Original Sin 3 out of this game but if that's what Larian turns it into obviously Baldur's Gate fans are going to be disapointed. I think Larian just needs to let this be Baldur's Gate 3 and save all of their DOS3 ideas for DOS3.