A 4th axis addon is probley the most simple thing you can do to your machine. Get a rotary table. Take the handle off it. But a timing belt gear inplace of the handle. Make a bracket for a motor to bolt next to it. Put a timming belt gear on the motor and connect the two gears by a belt. Hook it up to a drive and set your setting in software. Bolt it to the table. Square it and plumb it. Tail stock can take some thinking. I built a adjustable slide with a tig welder all thread 4" tube and 2" tube. It works but not great.
A cheap option is to go to harbor freight and buy a $69 wood lathe. Take the motor off and replace it with a stepper or servo and a timing belt. You would then probley need to do like me and take a angle plate from enco and mount you r spindle horizontal. Change the Z and Y around and then you can do much larger pieces..
Donny
www.whiterivermfg.com