Cousins to the Wiz isn’t impossible, but it is very difficult if he signs for the max or within a couple million of it. For example, if the trade was Otto Porter for Cousins straight up, Cousins could make no more than about $25.5 million in year 1, and the Wizards could have no more than 13 players on their roster without making additional moves, as they would be subject to the hard cap. Meanwhile, a straight Cousins-Porter swap puts New Orleans above the luxury tax with only 11 players on the roster, so that’s not ideal for them either.
Furthermore, if Cousins negotiates the max, the Wizards would have to send out at least $6.5 million in salary (again leaving them with a 13-man roster). New Orleans can’t take on that extra salary themselves, because they can only take back $27.2 million in the deal due to Base-Year Compensation rules, and Porter makes a little over $26 million himself.
All this is to say that a Cousins S&T with Washington is a very difficult thing to negotiate, and will likely require at least a third team to help out. So I doubt that this is a close-to-done deal 5 days before teams can negotiate with players.