How much effort does it take to cut the game's ties with Metroid in legal aspects then?
Changing a few names is easy, while original graphics can easily be defined as the author's own works. And since ideas are not copyrightable, most if not all mechanics can be preserved. So it mostly comes down to the graphics of enemies and Samus and some other things. And if enemy graphics are original and don't clearly resemble original design, then they can be preserved too.
Anything I missed?
BTW if anyone wants to play a joke on this turn of events, he could draw an icon '2-10-1' (homophonic pun) on a sinking ship in a Metroid (or whatever) hack.