RT. Just because you know you couldn't cope, does not mean you know others can't. If this story is anything to go by, they clearly can.
Referencing failed UK adoptions is quite I relevant, given this family have been adopting since the mid 80's. The only failed adoption mentioned, being that of two children which could not come to fruition due to a law change.
This, immense, beautiful family all seem happy and healthy. I would imagine (in contrast to your imaginings), that their home life, while not necessarily conventional is a lot of fun, supremely supportive and close.
With such a massive amount of support, I would imagine those with 'complex special needs and psychological issues' would absolitely thrive, rather than flounder.
What an amazing upbringing!