RE: Neale
I disagree about there being a better way already. DC/BLDC/AC servos or any none stepper based servos will all have the same fundamental flaw compared to a stepper. Because they have very low 'steps' or none at all, they have to microstep, and microstepping is fundamentally bad for torque and it's not great for positional accuracy either. Effectively it is running the motor backwards and forwards at high frequency to achieve an in-between position, it's not hard to see the flaw there. This means even the best controllers in the ideal scenarios are going to be at best +-1step, more likely +-10steps and much worse under a changeable load. Any change in load even 0.000001nm is enough to move the motor slightly out of step.

Add in a gearing system with backlash and it will be all over the place under a changeable load or direction changes.

If you have a really high count encoder the problems are minimised but it's really only bandaging the problem.

However if you had a stepper with many phases you could use full steps and still achieve high resolution. You get none of the problems of microstepping, no oscillation problems and additionally you get a better torque curve than any single motor because the phases are running slower than the motor. For instance at 100rpm motor speed you get the torque that you would have got at 50rpm with 2x the phases. Consider 5 motors, 1000steps, 100rpm torque at 500rpm. You get dead on accuracy no +- nothing and it would be held at that position no matter the load(assuming you don't have too big a load). Clearly this would be advantageous.

Don't take my word for it lookup 5phase stepper motors, the benefits are clear and I believe it would only get better with more phases.

RE: JAZZCNC
This brings me to JAZZCNC point. The only real downside to this (other than building the thing in the first place) is needing a custom motor driver. Which is beyond most people yes but it's not impossible. Even a lowly £10 Arduino has the hardware capability to control many motors, more than you would need and the code has already been written, at least for 5phase anyway, it's pretty much copy paste to add more phases.