I think that if you do read the OP's post he has a pretty good argument for why this change should be a good one. They have a rule so that you cant "buy" the league playoffs that lead to the B3 or in lower leagues promotion. And in the B3 to make buying a title much harder. But no such rule apply to the tournament so anyone can freely buy that trophy if they want. And i do like the idea to have to sacrifice something to win in the other. It gives room for good tacticians to shine a bit more then those that just play their 5 best every game.
I don't like the idea. I don't think it is currently unfair at all. People seem to be complaining that their opponents can buy great players before the match, but there is absolutely nothing stopping you from doing exactly the same. Neither team is at a disadvantage. In fact, having this allowed makes the game more interesting as you never know the lineup until just before the game, also, it means that saving up money is important because it allows you to do this.
If this suggestion gets implemented, then I wouldn't be surprised if people start suggesting that the teams should be locked in from the very first league game because "it's unfair that I am in fourth place and the guy in fifth place just bought lots of high salary players and is going to overtake me". It's just whining at the end of the day.
Under the current rules, the playing field is equal, and there is no reason it should be changed as it isn't currently unfair. The only argument someone could present in support of this idea is the realism factor, but that isn't an overly strong argument as there are 10 day contracts for the NBA for players not part of a team.