Hi eric, if I understand you correctly you can do something kind of similar currently with the Draw curve > Freeform > Control points . When you drawing with that command if you hold down Ctrl when you click a point it will be a "corner point" and behave like a polyline if you keep holding down Ctrl. When you're not holding down Ctrl you can draw a curve freely.

I guess you're talking about drawing arc pieces though instead of freeform curve pieces?

- Michael