Like you, i had a $1,000 ford ranger 4cyl 5-speed and it was a great vehicle to learn how to drive in. I could never really go fast enough to kill myself and that was a good thing. But because i was an enthusiast I worked and saved as much as I could to get my DSM (96 eclipse gs-t) and I was so proud of that car... worked on it constantly, washed it religiously and improved it in every which way I could. I just don't see a 16 year old kid having the respect to handle, maintain, and appreciate this much car. Sure it doesn't have alot of hp on paper but this would have been considered a pretty damn fast car when i was first driving. And with others have mentioned, it has a pretty aggressive set-up, suspension wise, and he could easily lose the ass end and end up in a tree. These cars beg you to drive like an ass-hat and it takes maturity not to....and i know if i had this car as my first car (and didn't pay for it) it might not have ended well....
please get him something he can grow into and learn how to fix and improve. Start off on an affordable platform that has aftermarket support and that will grow his inner-enthusiast more than anything. Growing up it wasn't about whose daddy bought them the fastest cars (those always ended up wrecked...almost all of them, i have many stories) it was about the kid who had the $2,000 civic that he did a b18 swap and gutted the interior and set up the suspension and did all the work himself....he was the one that got the respect.
Thanks for all the replies and opinions here. Very thoughtful responses. This argument above is probably the strongest point against the FiST. And it is not so much about the ST being a good or bad choice, but rather the experience of earning and doing something yourself. I do not want to unintentionally spoil him, but rather support his enthusiast interest (as we both like cars and it is fun to share the interest and hobby). I am planning to take him to some HPDE track days so he can learn car control on a track, and hopefully also learn to respect speed and not do that on the street.
Practically, I already have the FiST. It isn't my daily driver though. If I did trade it on something slower/cheaper for him to use as a first car, I think we'd both be shopping for something more sporty in no time. But I do completely get the meaning of having him learn, and then search out a car that he wants to earn and make it his own. He does like the FiST but he doesn't see it in the same way as a RWD sports car, so that search might happen even if he does start with the ST.
My first car was a $1000 RWD Japanese coupe that maybe had 100hp. It was very slow and I still managed to put it in a ditch. I don't think it is the additional power of the ST that makes it any more risky, but rather the handling that gives a sense of security and encourages faster driving. That is both a good and bad trait. He will have to learn to respect the car, the same as with any car. An ill handling RWD vehicle, like an old pickup, is arguably more dangerous as it is easier to lose control. At least the ST handles well, is very controllable and forgiving, and has good stability control (even though it is defeatable).
Lastly, if I were to look for a different car for him to start I would insist on something of relatively recent model year, for safety reasons. Modern car crash protection is much better than cars even 10 years ago. So if I looked for a good used Civic, for example, I'm not sure it would be a whole lot less $ than the value of the ST I currently have.