Any worries about Mete's ability to adjust to a long season and to the NHL are invalid and completely short-sighted.
For one, he's 19 years old. Stamina-wise I'm not even worried about this. He just has to keep playing to his strengths and playing with Weber should prevent him from getting abused repeatedly.
As for adjusting to the actual pace of the game; it should not even be a concerned, as he's probably as quick as any player in this league. He'll make mistakes. But in preseason everytime he did a bad play he came back right after and fixed his error with his skating.
There's also the Weber factor. This guy will learn a lot of things playing with Weber. From positionning to stick play and board play. He'll actually learn more there than in Juniors. Plus, him getting leveled is not as concerning as one would think. These shorter guys are harded to knock down. They have a low center of gravity and it's hard to actually catch them with a huge hit as they usually roll under the hits. McCormick pushing him after the play won't change anything about that, he just has to be careful about boneheaded players like this and he'll be fine.
To judge if a player is ready I like watching his decision-making ability, his poise, and his authority with the puck. He passes with flying colours in each of these area. Positionning, stick work and other details can be learned. But confidence, poise and Ice-Q are things that you can't learn. You have them at birth, and you develop them. Some quicker (Mete), some slower (Hudon), some never do (Beaulieu). The fact that he's quick as hell just gives him a nice little buffer to fix the mistakes he'll probably make, until he adapts to the quickness of the NHL.