Lots of us that play with TurboCad aren't employed as Cad operators and have minimal drafting experiance. From my standpoint, I took one drafting class in HS in the early '70s, and another in college shortly thereafter.
Something I think would be good would be how to incorporate ANSI/ASME drafting standards into your CAD drawings. The use of Geometric dimensioning and tolerancing when drawing a CAD model. Also the use of welding symbols.
Basic workflow, layers, exploded drawings and animations to ensure there aren't any interferences with assemblies. I find this to be chanllenging, remembering what layer I put stuff on.
More details on the TurboCadCam plig in. How to interface it with a machine running Mach3 as the controller. Small CNC machines are now in the hands of hobyists, so a tutorial demonstrating the tools in that plug in directed to the Mach3 control software would be a great plus.
I'm sure some of this my be in your other tutorials, but not sure as I haven't taken them.
Most of my stuff is mechanical also, steel tube, wood, and sheet metal structures along with detail parts (airplanes).