>>Doing it for a single individual is where the problem lies.<<
If that's where you see the problem, then there's no problem. There's nothing in the constitution prohibiting such actions, and I don't think either this court, the Court of Appeals, or the Supreme Court is going to hang any unconstitutional ruling on the idea of Congress having only expressed powers (i.e. can't do anything that's not expressly permitted). THAT would open up the floodgates of litigation to virtually everything Congress has done in the last 40 years. All one needs is standing to bring a case, and you're in.
It is where I see the potential Constitutional problem. The House also saw a problem on these grounds, which is why their original language was more broadly applicable. The Senate wanted the bill narrowly tailored. That's what the so-call Palm Sunday compromise was all about.
Indeed it would. And that would not be a "Bad Thing". If the federal courts reject the law on that basis, and Terri dies, she will not have died in vain if those floodgates are opened and all the unconstitutional laws are overturned. But you're right, it's not going to happen.
It's a very rare occurrence when the courts overturn a law on the basis of Congress not having the power to pass such a law. The first Gun Free School Zones law comes to mind, but all Congress did was sprinkle some more "Interstate Commerce" pixie dust on the law and pass it again. AFAIK, the second law has not been challenged and certainly it's not been overturned.