Suggestions in 2 steps:
1. Add a PEAKED modifier key to the "add point" tool.
2. Something like this:
-set a point at (X,Y)
-set curvature defined by modifier key
-is there another active point?
-if yes, connect these points.
-if this tool is placed on an existing point, behave like the transform tool.
# 1 should be pretty easy, but even this will take me several hours to get into it, so this is a suggestion until I have enough time to get familiar with scripting basics (2007?)
#2: Why am I so keen on this? The "add point" tool works best with a mouse, because it is easy to keep position when lifting the mouse button.
I usually draw with a tablet. Here you always lose your position slightly when you lift the pen, having to relocate before drawing the next point.