Definitely 4. It was so much fun to abuse the hell outta that guy. Also the reason his head looks different in 4, was because he had a light surgically transplanted in there.
I like your thinking. I was playing a lot of Metroid Dread a while ago and was thinking the team behind it would make a killer WL3 style game.
Would be pretty cool to see how that could look today.
Would you want the game to be more focused on speed like 4 and VB? Or lean closer to puzzle solving and exploration like 2 and 3?
Honestly, I could go either way. As long as they're fun and not too slow or easy.