I have a few questions,
1) Does Marner have to play in the CHL next year or can he play in the AHL?
2) If Marner is not allowed to play in the AHL can he play in Europe for a year?
The Marner situation is not like Nylander in that he doesn't have any European heritage/roots nor history of playing overseas that this would be a logical decision for his development for Leafs management to chose as a valid option. Since Marner has signed his ELC already the Leafs not Marner control where he will play.
Even with Willie the Leafs brought him back to North America as a 19 year old A.S.A.P to get use to playing on the smaller ice and in a style more closely related to the NHL. The Euro game on big ice is a vastly different game to NA style of hockey.
Not sure why fans think another year in the OHL as a 19 year old will hurt his development. Max Domi another former Knight is a great example of a 1st round pick that was sent back to junior for 2 more years post draft and now look at the impact he is making at the NHL level 14 games 7-6-13 points (2nd in rookie scoring). If Marner hits the NHL running having the impact that Domi is having that would be great. IMO
This is up to Marner to make sure he works on his development on and off the ice this season so that he pushes for a NHL job next year.. If he fails than its 99.9% chance he returns to London of the OHL and Mark Hunter's team for further development.