I am getting into this a bit late on - but there are a few things I am puzzling about.
The first was the comment in the first post - "How to make Mach 3 turn an axis for which there is no DRO"
I cannot see why you do not just put a DRO on the screen for the turret - marked turret. It only needs to be one or at the most two digits long.
As far as turning the toolholder on a stepper, then if you set the steps per unit at the number of steps it needs to turn to from one tool to the next, then the commands are simple G0 A1.********* - G0 A1 where ********* in the fraction you need to overun, and A1 is the locked position of Tool1. The machine would then overrun the position and back up to lock the tool. The DRO would then show the number of the tool in the holder.
I would make the home position the position of locked tool 0, but I cannot see why you need three indicators - one would do if you have the contrallability of steppers.The logic of choosing the tool numbers is fairly straight-forward, if the axis is continuous.
I know Hood has already done a lot on this - but am I anywhere near the right lines on this, I might start on a turret myself, soon.
Jim.