Yes that's a game changer and would be happy if Rust had to be the sacrificial lamb. Kahun and Tanev bring Rust like qualities so it can still work. I don't really want to move Bjugstad unless they feel confident McCann can be a center. If so, then that's fine with me too.
Jake-Sid-Kahun
AG-Geno-Hornqvist
McCann-Bjugstad-Tanev
Simon-Blueger-ZAR
Dumo-Letang
MP-Schultz
Gardiner-Guds
That would be pretty impressive overall.
How about this for a crazy idea...
JMFJ, Bjugstad, AND Rust for Lowry
Sign Gardiner
The Jets have the cap and roster space to add all of those guys. Bjugstad and Rust are pretty good, versatile players and on reasonable deals. Easily flippable if things go south for them. Can't really justify them wanting JMFJ, but they did just lose Trouba and Meyers. Maybe you could trick them into wanting a 'tough', 'minute eating', 'veteran' like JMFJ.
For the Pens, it solves their biggest weakness (JMFJ), their second biggest weakness (LD), and depending on who you ask, maybe their 3rd biggest weakness (3C). I personally don't have a problem with Bjugstad at 3C, but I do tend to like the 3C's who eat the tough minutes, PK, etc. like Lowry more. With that much cap going out, depending on what Gardiner gets, you might even be able to add another winger.