If the player takes, so taking less cash so 2K needs to make adjustments for how players accept contracts beyond just cash, the display looks exactly the same as it will now where it says"approved" and you'll be able to adjust that to not sign him, but rather it would say"approved - sign-and-trade." Once you reach next, MT NBA 2K21 requires you to the trade screen and a message appears that states"to be able to finish this sign-and-trade, you have to complete the trade" or something along those lines.
Then you have to put in wages or TPEs to make the trade work, which would remain the same as it is now. The part that is key here is that the team would need to be put to accept, so the transaction logic could be out the window. So if you are earning a man who's earning $20m, you are able to send out five garbage players along with another round pick and the opposing team will take it.
The toughest part would be making the adjustment where sign-and-trades hard cap the receiving team. The easiest route is to ignore this, which NBA 2K21 essentially does. Another route, which honestly should not be challenging but I might be naive, would be to then trigger the hard cap at the luxury line, or high-end but I do not think 2K has got the nickname in NBA 2K21. In case NBA 2K21 does tough cap you, a message ought to be appear that states"as a result of this sign-and-trade, you are now hard capped in the luxury tax. You have to remove $XM in contract to get under the tax line"
At this point, you'd be on sent to your roster page and would have to waive/trade players to become under the tax line. NBA 2K21 would have to follow these steps, though transactionally it does not do that in real life - the Warriors needed to exchange Andre Iguodala to the Grizzlies before completing the ss with Brooklyn to get under the hard cap, but the arrangement of which the decisions were made was in reverse. I expect that is informative and makes sense. I really don't think it should be that hard to implement in NBA 2K21 but I'm not a coder or game manufacturer so that I could simply be naive.
Makes sense to me, although I doubt 2K puts that much work into a non lucrative mode. The transaction logic might mess it up too. Since players would need to have a motive to want the s+t (ie more money, combine with another star, get to a contender). Along with a reason to do it also would be needed by the trading team. Cap would not be super difficult to Cheap NBA 2K21 MT Coins get around since it will be off season and most teams could have cap and I believe they can even go over since they'd technically sign a participant with bird rights to maybe receive a player they didn't have bird rights to (I believe that is how the KD/Dlo trade occurred too but I might be wrong).