The one year TDL thing is a common one and it doesn't seem like there's an issue with it.
I think it depends on the scenario going forward. This year was one of the first where we saw sign and voids (Galchenyuk) as well as sign and trade (Tkachuk). As more examples of these show up, I wonder if more teams may find the circumstances to make such a transaction possible.
I think signing a UFA and then trading them rapidly could occur, but I don't think you could get away with it if your intention was to trade immediately and not try to leverage their contract status at the TDL. However, I guess this could be possible if a player suddenly had family they wanted to be around (illness) and it was either retain and trade to a specific location vs the player go on an extended leave of absence. Maybe something like that? (ie: Heart attack of a family member a few weeks after signing as UFA?) But I assume teams would try and ask the league if it's allowed prior to doing it vs just doing it and asking for forgiveness.
a 1 yr rental you sign you can trade at the deadline. If something personal came up like parent cancer diagnosis they might ask to get traded to a closer city or do a contract termination under mutual agreement.
teams aren’t retaining salary for family stuff. They could trade the player.
three league can give waivers on situations where player X who signed a 6+ yr contract with team Y and a wife/child/ parent health issues come up that try can take a leave of absence where the contract is suspended or it comes off the cap for that year they are out. In some ways it’s similar to not getting paid due to a non-hockey injury.
teams are allowed to do long retentions on players they had signed and played for 1+ yr and realize it’s a bad fit. We saw it with OEL, Hayes, and Kessel.
league will step in of the smell test isn’t passed