This might be a bad take and I know that it is going to go against the premise of this thread, but I feel like the value of centers is actually dwindling. Not that wingers are becoming more valuable or anything, just that it seems teams are going to more of a 3 forward positions rather than a center and 2 wingers scheme.
A lot of teams are starting to play 2 centers on the same line or simply 2 people they feel comfortable winning faceoffs. Those teams are trying to get an advantage or at least limit a disadvantage by keeping players on their strong side for faceoffs. However, even if a center takes a draw on their weak side, would they not have at least a slight advantage against a winger? San Jose has one of the best faceoff winners in Joe Pavelski, yet after the Evander Kane acquisition, it was Kane who would take draws on the Left Wing side, and before Kane it was Thornton. Vegas has Marchessault taking faceoffs on the right side and Karlsson on the left. The list goes on
And if you are thinking "those are just faceoffs, once play begins players have their defined roles of where to be based on their position." That is becoming less true now as well. Forechecking schemes used to be 1 winger goes into the forecheck, one stays close of a quick pass or create a turnover and the center remains high to stay in defensive position. Now it is becoming F1, F2, and F3. The first person in no matter their position is F1, second one is F2, and the last is F3.
That is how it works in the defensive zone these days now too. The first guy back is F1 and covers the slot or assists the defensemen. The 2nd and 3rd stay relatively high in the zone to defend passes to the point.
Because of the free flow nature of the game, the 3 forward positions have been used to describe where to stand during a faceoff, but with so many teams trying to keep players on their strong side for draws, positions are becoming even less relevant.
I wrote all that to say this, the Leafs do not need to turn Nylander into a center. Keep him as he is, if you want him on his own line away from Matthews and/or Marner that is fine. He can still take faceoffs and stuff, but play him with a stronger player like a Brown or a Hyman. Nylander can win draws but with a stronger player the team can have that player help control cycle games and down low play. Because of the F1 set up, it is not going to be Nylander down low the whole time anyways.