Agreed! The ability to draw complex wave patterns with high resolution would definitely be tedious and not very pragmatic. But in applications where complexity and resolution are not a factor it could be quite helpful. Square waves are good a example of this. It is either on or off and therefor quite easy to draw. Possibly even saw-tooth waves.
Smoothing would be a nice feature. A way to fill in the gaps and "smooth" the gradience between the steps of the curve drawings.
Matrix definitely works better as a step/pattern sequencer, but I was just trying to use it outside the box a bit. It's annoying when you have to add a whole synthesizer just to gain access to a LFO for CV control. I know that there is a LFO rack extension, but that will have to wait for a bit.