Nice try, but that’s an 18 man roster, not 21, and you need at least 18 skaters + 2 goalies to have a level opening day roster

It's a 21 man roster and as of 5:00 pm EST on the 9th not opening night. IR players count as roster players, the 18 skater 2 Goalie rule applies to game night rosters. Game 1 roster will have Dvorak, Wideman and Price on LTIR with RHP, Slaf, Harris, Wifi and Barron on the game roster. There is a huge distinction between game 1 roster and opening night roster.

IR players have literally never counted as roster players…

Sorry, I apologize, I misinterpreted the rule. You are correct, still an easy fix though

You can simply scratch a player rather than place them on the season opening injured reserve list, then move them to IR or LTIR later if they qualify. Being injured doesn't disqualify you from taking a roster spot. You are free to evaluate and manage your players as you choose so long as you are following the rules and I'm not aware of one that prevents you from activating an injured player (otherwise players playing through injuries wouldn't exist).

Pretty sure we're just looking at paper transactions that still make this roster work legitimately.

Now a team may not want to do this with a LTIR player or for other reasons, as it may not be as simple or beneficial to manage, but I don't believe it is explicitly forbidden in any way.