For starters, someone would have to prove standing to have a case. And this law only targets the Office of the Presidency, so only a President could challenge it.

And if Donald Trump or a future wannabe-dictator gets elected, they'd have the exact standing needed to make such a challenge.

However, since we’re wishing for the Dems to play hardball, Article 3 Section of the Constitution says this:

In all the other Cases before mentioned, the supreme Court shall have appellate Jurisdiction, both as to Law and Fact, with such Exceptions, and under such Regulations as the Congress shall make.

The Supreme Court usurped that power for themselves in (I belive) 1803 and hasn't been challenged in 200+ years. Since then, if the SC makes a ruling, Congress has historically said "aw, shucks", and that's the end of it. At most, you'd put both branches of government into a conflicting "You've made your ruling, now let's see you enforce it" scenario which would bring us dangerously close to civil war.

Also, how would it work out? Trump gets into office and wipes his ass with the "No Kings Act". Do you honestly think for half a second that Congress is going to impeach, convict, and remove him any time soon? Because if so, I've got a whole lot of beachfront property on Mars that you may be interested in. The only other way would be.....through the court system. Which would end up at.......the exact Supreme Court, the exact same six judges that just gave him those powers in the first place. I'll let you sit there and think over how that would ultimately end.

Or, the SC could go the "malicious compliance" route. They let the NKA stand, knowing full well Trump is going to ignore it anyway, and knowing impeachment and removal is nigh on impossible in today's political climate. So Congress tries to sue and gets "well golly gee darn, you just got finished telling us we can't interfere. So he's your problem now. Good luck." Now what?

Or later in the future. 10 years, 20 years from now and the SC somehow gets rebalanced into something legitimate. Except now it's congress that are openly corrupt. Do we really want a situation where our SC would be able to do exactly nothing as a corrupt congress runs roughshod and starts further narrowing the oversight of a non-corrupt SC while passing more draconian legislation? It becomes a situation of being careful of what you wish for. You might get it.

Congress could literally pass a law limiting the powers of the Presidency, and also declaring that SCOTUS doesn’t have the jurisdiction to hear any cases regarding it. Congress could also create a whole other court system solely to handle challenges to Presidential authority and there’s nothing SCOTUS could legally do to stop it. (Not that Roberts’ corrupt Court cares much about the law, but still.)

Good luck getting the general public to accept that there's literally a completely different legal system for some people and not others. I don't care who it is or what the purpose of this secondary court system should be, you will (and should) never get the general public to accept setting up a secondary court system just because some people don't like the rulings of the primary one.

Would you consider a secondary court system headed by Aileen Cannon as the Trump-appointed "New Supreme Court" head judge legitimate? Of course not. The same applies in the other direction. The idea is absurd on its face and turns our justice system into a glorified game of Calvinball.