None of us can truly say we have a realistic roster because we have no idea what's going on beside Sakurai's head. However, I must agree with him (along with just about everyone) in saying that you're choices are less realistic than ours. For example, Ridley is still absent from your roster while you have Starfy. Could it happen? Yeah, sadly. Should it happen? Not in a million years. Is it likely to happen? Not even close.
Facts to back up that comparison:
Ridley is not too big, insanely popular, and the most iconic villain of Metroid.
Starfy is pretty popular, but it seems to be limited to Japan and still nowhere near compares to the likes of Ridley, Mewtwo, K. Rool, etc. The starfish also seems distasteful when trying to think of a good moveset.
We've fully explained each of our choices to to convince each other that our choices are realistic to some extent. For example, Masked Man (who is in my roster) isn't likely, but he makes a ton of sense based on the way I built the roster (meaning it would be strange if he were included and I hadn't built the roster with my method). As a proposal, I've gotten a lot of praise as my roster is definitely unique and still works out well as a balanced roster.