Why to set you master tool off the probe? Any reason it could change its position? I was actually more thinking in the way of making a macro to take advantage of the electrical probe and set all the tools automatically with respect to the master tool. You could probably use temporary DROs to store the true position of the master tool before touching off the probe and then touch it off, override the X and Z DROs with say 0,0, and set all the tools with respect to that, then return back the stored true position of the axes - all in a single macro. This way you don't need to reset your master tool each time.
If you do it this way, and considering your machine's repeatability, I think you don't even need to machine the part each time and measure it.
Hope it makes sense...
Daniel