I would let him sit out the year, find gainful employment outside the league and let him build some hype and trade him later if it ever came to that. The December 1 deadline is so artificial and makes me laugh at some of the returns Sportsnet is throwing out there. Let him sit, let him make the case for being the "best player not in the NHL" while dominating in the KHL or something and make a decision next summer.
The other thing to consider too is that while Nylander can't rejoin the NHL after December 1, we could still probably deal him to a bottom feeder for a trade deadline return. For example, imagine a team like the St. Louis Blues were moving on from Alex Pietrangelo (to use an appealing star player) and are tanking for the 1st overall. They could still pick up Nylander in a futures package, not get any better to hurt their rebuild and tanking to boot or pay him the rest of the year.