Kallgren and Petruzelli buy us time to evaluate our goaltending needs to say nothing of Jack Campbell. And should Jack Campbell make it to free agency, I believe he becomes the most sought after G FA.
Nylander plays a secondary role at a ppg and in the last two playoffs has also been a ppg. Then there's the advanced stats particularly Nylander's offensive zone entry numbers...and then there's the unlocked potential; I think Nylander leading a team would be a top tier point producer.
And then there's the intra-conference trade element. Not sure I want to trade William Nylander to that Rangers team that seems to be getting scarier and scarier.
If we were going to trade Nylander in conference, I'd rather your desired combination of winger and goalie be Batherson and Forsberg from Ottawa. Cost-controlled a little more proven, a heck of a heavier lift in Ottawa to present that franchise as any sort of ongoing threat when they come to Toronto.
So for the model proposed: Keep Nylander.