I think a Pettersson trade could work cap-wise if you can do something with Fleury's deal this summer.
Greenway + Rossi + Lambos + 1st
Kaprizov - Pettersson - Zuccarello
Boldy - Eriksson Ek - Hartman
Duhaime - X - Foligno
then
Kaprizov - Pettersson - Boldy
Ohgren/Yurov - Eriksson Ek - Hartman
I'm a little more reserved about trading prospects than most people given the situation we're in. His contract situation makes me nervous. One more year on it, and I know he's an RFA at the end, but I don't want to get into a situation where he's looking for 11M+ and we can't give it to him so we go to arbitration and then end up not being able to keep him. For me, this trade would be contingent on him having a long term (7-8 year) deal already in place, which can't happen prior to July 1st.
Chychrun would be an incredible addition to a contender. Easily a top pair pair two-way guy and he's a great person too. His contract gives me pause too for the situation we're in. Only two more years, too early to extend him, not enough time to do anything with him without an extension. And would be expensive to acquire.
But man, if I thought we were in a position where it made sense to go after him, I would love to have him. Excellent player.
Bottom line, both Pettersson and Chychrun would be guys I'd be 100% fine with giving up actual value for, assuming we got to keep them longer than a couple years.