I don't have a servo on my knee, I was just giving an example of how EMC would see 2 servos acting on the same axis as a single axis to help explain how EMC can use 8 servos for the six axis. But just like a brake on a motor you could configure EMC to unlock gibs while moving the knee.
When starting a spindle syncronized move, EMC zeros the spindle counter on an index and synchronizes from there. The difference with a 2 spindle revs vs. 1 encoder rev is that the index only comes around once every other revolution. I bought a 500 line encoder for my spindle giving 2000 counts per encoder rev or 1000 counts per spindle revolution. So, in 1000 counts my axis can position can be 1/13" or 1/13-1/2" or any other standard, metric, or non-standard pitch is no problem.
In general I think a manual machine can be set up to out run a CNC machine but the advantage I see in a CNC machine is to use a few tools to produce many different shapes. For example on the lathe pawn program, there are various tapers and radius cuts. A turret lathe with form tools, etc could probably outrun a CNC on a setup but the CNC lathe could probably be hours ahead if you have to make 2 of this part and 3 of that part.
I was kind of thinking as a step between, using EMC to replace your control now and swapping out the steppers for servo's later. But, it doesn't seem reasonable to replace your existing drives with micro-stepping drives or anything like that for a temporary transistion.
I know what you mean, I prefer servos too. One thing I like about servos is that their torque is generally rated as continuous and goes up from the rating whereas stepper torque is rated as holding and goes down. I didn't know that the Emco lathe had ball screws, is sounds like it will be a very nice project for an EMC conversion. The hardware sounds great, just sounds like the control need updated a bit.
RogerN