I have a "back and forth" effect for my arches and I can set the exact time (in 50ms increments) that it takes for the cursor to do one back and forth cycle. The way you could do this in NC is to have a spiral in one direction, a spiral in the opposite direction and paste them back to back. (There's probably an even easier way to do this.)
I agree though, most of the effects on the wish list can be done utilizing Nutcracker's spirals and adjusting the speed accordingly.
If you want a gap of no color, I've had success making chases where I space the colors utilizing black as a color. For instance you could do red, black, black, green, black, black, etc.