I do not mean to be pushy but I hope you really are planning on adding a tool that enables you to place lone CPs . A feature like this won't hurt and it would leverage the already existing tools. The idea is you could add a lone CP , change the 3d perspective a little , add another one , and so on. And then you could draw along them to create a curve. It is very difficult to draw a curve while changing the 3d perspective simultaneously . I submitted an issue about it about a year ago.