I can't see the NHLPA going for that, unless the contract in 100% covered and not a "buy-out".
I think maybe they could soften the cap a tad and allow teams to trade for another teams unused Cap space. You could trade draft picks for space in increments of $1M: your upcoming 7th for $1M, 6th for $2M, etc. etc. up to a 1st for $7M. And that pick cannot be lottery protected. Teams can only add or subtract up to $7M, and you can only use your own picks in the next draft, so you can't trade something like 7 7th's to 7 different teams to get $7M. The kicker would be that you can't sell or add cap in trades in two straight seasons. The NHLPA would love it.
Another idea could be like a waiver draft type thing before the draft and then at the beginning of the season. A team would leave their non-NMC protected bad contracts unprotected and then they leave 10 "assets" (roster players, draft picks, unsigned prospects, pro-level prospects) unprotected. A team with cap space can claim a bad contract at 50% retained and in turn they get to take 1 unprotected "asset" as well. Or, they can claim the entire contract and choose two unprotected assets and get some sort of draft pick compensation from the other team at the end of the deal which would be based on some formula around the money and term left on the deal (IE like claiming Lucic's full contract would give the claiming team a high Oilers pick in 2023). The pick compensation would be a reward for carrying out the full term of the deal. If the player is eventually bought out or traded, the pick compensation is voided.
That could be the annual NHL yard sale...