I wish I had a more sophisticated understanding of mental illnesses. (I'm a molecular biologist, so, anything bigger than small animals are out of my range of knowledge.)
I find it interesting that you say there's a correlation between the level of violence and the level of intent. It seems like there's more suicide prevention efforts on more violent means, such as BASE jumping without equipment, than less violent means. (I say that somewhat casually as my way of dealing with it. Came across a fresh one at night on a highway. Couldn't find a radial pulse. Couldn't find the carotid because the neck was so far displaced. Messy.) They spend millions putting up anti-jump barriers only to have them go to a different bridge. Seems like if the violence is high, and thus intent is high, the money is better spent on other forms of prevention than temporarily delaying them.