This isn't that complicated. No cap after the trade deadline. All trades go through the NHL for compliance with cap. So any trades or contract signings some short period of time (say 12 hours) before the deadline expires, the NHL will allow those trades to exceed the cap.
This is where your plan falls apart.
1. When you say "no cap after the trade deadline" you really mean "no cap some 'short' period of time before the deadline".
2. 12 hours is 3am Eastern. GMs are not going to be sitting up until 3am to hurriedly cram through trades, even if you reference they could be "bidding against all the other teams that will have their cap restrictions lifted post-deadline". Calls to players have to be made notifying them of trades; league personnel have to verify contractual protections for players, agents have to be involved, trade calls have to be held with all the parties involved. And any subsequent trade involving those players, prospects or picks can't be done until that trade call is done and everyone is in agreement, just in case something goes awry. No GM calls up another GM, proposes a trade, and everything is done in 15 minutes.
So ... 12 hours is unrealistic, for all this trading you imagine is going to occur sans cap. Why not make it ... say, 24 hours? And if you OK 24 hours, why not 48 hours? 3 days A week? The fact is, the moment you say "I'm willing to let a cap not exist prior to [any point in time you choose]" you open the door to the cap not existing at all. Which, as I've explained 112,003 times previously, the owners
are never allowing that door to get pried open even the tiniest bit because it then becomes leverage for "... so let's get rid of the cap entirely" which they are
NEVER doing.
In your LTIR example, there's only a slight benefit to trying for the loophole. The LTIR team could theoretically trade for a player earlier, but they would also be bidding against all the other teams that will have their cap restrictions lifted post-deadline. Maybe the LTIR team offers a more to acquire said player earlier, if so good for them, I have no problem with that, they still had to outbid the other teams.
You've "solved" the "problem" of teams stashing players on LTIR and having them back for the playoffs - which is the "problem" you set out to fix - by ... eliminating the cap, so that everyone can spend as much as they want on a team come playoff time.
I'm not eliminating the cap completely, just ... some 'short' period of time before the trade deadline. And, then teams - I'm going to go out on a limb here and say high-revenue teams - can use their financial might to spend as much as they want on players at the expense of other teams - again, out on a limb, saying these will be the low-revenue teams - which will tilt the competitive balance of the league.
I gotta applaud you here, I didn't see "I'm going to take the backdoor route to 'get rid of the cap so high-revenue teams can use their money' coming. But I'm still going to tell you, it's
never happening.
You still need the floor in place so teams aren't wholesale selling players and to still enforce some cap limitations. Removing the upper limit just gives teams more freedom to maneuver. Average league salaries for teams are already above the average, not sure what your point is here.
Teams can wholesale buy, why can't they wholesale sell? It would give teams
even more freedom to maneuver. Where average league salaries are is irrelevant; what's relevant is how much flexibility you want teams to have to make moves. As soon as you open the door to "make whatever moves you want, they're all legal because there's no cap" it is inconsistent to then say "whoa whoa whoa, not
all the moves you want to make - we gotta have
some integrity in this process."
And no there's no free license to spend because teams will still be restricted by the cap next season and most contracts have already been signed by the deadline. The pool of players available for trade and their contracts are already set, it's not like a team can just go out and sign someone to a one-year $15M contract, unless that player was in some weird injury situation and held out until the deadline. If so then good for them, again no problem with this as all other teams can do this too.
There
is a free license to spend, though. You're just trying to thread the eye of the needle from 1000 miles and say "but the cap goes back into effect next season" and the
very first question the NHLPA will have is "if you're OK with the cap going away before the trade deadline, why can't we just get rid of it completely?" I'm going to let you read back through my prior comments and see if you can figure out what the owners response is going to be to that.
I'm going to say this to you and everyone else trying to come up with a "solution" to whatever "problem" you think exists: Go back to the start, try to figure out what problem you're trying to solve, and work on a solution from there that (1) actually fixes the problem, (2) doesn't create new problems that you then have to solve [or come up with solutions to those problems], (3) isn't as complex as a Rube Goldberg machine, and (4) would seriously be considered by both the NHL and the NHLPA - which means
do not say "well, owners would like to spend more" or "well, the NHLPA is concerned about players being able to win a Cup" because
neither of those are true.