It’s really circumstantial. I don’t think they would need to be any better at goalkeeping than the best ones already are; the odds would just have to break right for them. They’re obviously not given entirely on merit, so you just have to have the best story, a lot of which is out of the individual player’s hands.
One thing that will help a lot is Messi and Ronaldo are pretty obvious outliers, and they won’t be competing for these forever. Then it just becomes a question of who can rack up the most accolades in 12 months without some outfield player having similar success and also scoring 50+ times. And to that point, even Lewa is what, 33 or 34 now.
Maybe Oblak could do it if Slovenia miraculously advanced all the way to a Euro Final (extremely unlikely), and Atleti won a treble without any of their strikers being out of this world (not unlikely).
Or, it seems to me that, let’s say, if Mendy merely played very well, and Chelsea won the league and France won the Euros (and let’s say Kante missed six weeks, while we’re at it), in a universe where Messi and Ronaldo didn’t exist, that wouldn’t be too far away from a possibility, would it? That was basically the Jorginho case; eliminate everyone who didn’t win each trophy until you were left with just one guy. He managed a third place without being anywhere near the kind of player who grabs all the attention.