I absolutely disagree with two of your assertions:
Schiefele on the system: the top line has almost always played a dump in retrieval style game. Schiefele played maybe his best hockey as a Jet in the first have of this season in the exact same style.
Additionally, they played essentially the same system in the "pack of wolves" season, and he was incredibly productive in it.
It's more likely that he's worn down by the grind of the season and how many minutes he's played. Not only does he play the most minutes of any forward, he's playing the hardest minutes, AND other teams key in on him as they know he stirs the drink for the Jets.
The solution is to have 3 scoring lines, and allow Schiefele to play a bit less and under some more favorable matchups. Id be looking to rest him in the last 7.
Secondly, we're too small:
We're one of the bigger teams in the league. One of the things I hear about the Jets from other teams broadcast teams often is how big and physical we are.
That doesn't mean big hits all over the ice. You hit when you don't have the puck. The Jets use their physical energy for protecting the puck, turning it over, etc. They don't play a bullying style.
I will say I wish the Jets finished their checks a bit more often because there is real benefit in that.