This was clearly mentioned as an issue in my original proposal. I never ignored him having to change his mind and waive his NTC.
The Rangers have almost no money coming off of the book next season. Glass and Pirri combined could save them a few hundred thousand if they replaced them with cheap 2 way contracts. That's all really. The cap is far from a guarantee to go up or even stay the same. This season the cap would have declined had it not been for the NHLPA once again agreeing to use their escalator. The Rangers willl have to re-up Zibanejad at 4M-5M per, then there'll be a few other players who will command raises like Lindberg. They'll likely have to cover Vesey's performance bonuses (potentially nearly 3M) that with only 1.5M in cap space right now could carry over to next year. There are also players like Brady Skjei who might earn performance bonuses if they play a big enough role. I think you're underestimating how tight they could end up being to the cap.
I never denied that Nash was still valuable. I never painted him as a pure cap dump. I stated the Sens would still have to give up something valuable with MacArthur like a 1st + +.
The point of the trade is that cap wise it accomplishes different things for each team involved. Ottawa spends the money wasted on MacArthur on LTIR on an actual player via spending 16M on Nash over two seasons instead of nearly 20M in real money on Mac over four. The Rangers get about 3M in actual cap relief this season and next season which for this season is important because it'll prevent performance bonuses from carrying over to next year. So it isn't like adding cap this year is useless just because they've already fit their team under the cap ceiling. The other 4.5M in relief would be in LTIR.
If someone was willing to take on Nash without them having to take on a contract like MacArthur's, while still giving up a 1st + + for him, I think the Rangers would have traded him by now. Which is why I think it might be plausible that they'd pull the trigger. Gets both teams out of a bad cap/financial situation, but Ottawa has to add significantly because they are getting a player and they are getting the better side of the cap relief.
As far as the expansion draft goes, the Rangers will have to leave at least 1 decent forward unprotected between Lindberg, Hayes, and Fast. Ridding them of Nash's NMC let's them keep an extra one of those players.
These are all realistic sounding moves.