I thought of this for my now 18 year old, but the twizy is VERY bad in side crashes.
I actually spoke to the chap who tested it for it's insurance classification, excellent chap, but it is really bad. Although I have one, there's no way I'd put an inexperienced driver in one, particulalry a hormonal 16 year old!
I told him he could pick a group 1 NCAP 5 car, idealy with 2 seats. Stats show a lowe crash rate for boys with 2 seats, less "egging on" I suspect.