I just purchased an i1 Pro spectro, which I want to profile the i1 Display Pro against to improve color accuracy.
Perhaps you should tell us more precisely what you mean here. Are you intending to profile a display with both of them and compare the results? Or are you wanting to build a compensation profile like DispCal allows you to do?
Or are you wanting to analytically compare the colorimeter to the spectro and use the results to compensate for colorimeter drift? If so, this is too tricky to do outside of a lab with more sophisticated devices. Everything drifts, even your display during calibration. If you trust a spectro more than a colorimeter then just use the spectro for display calibration. Personally, from everything we've seen so far I don't think you have reason to worry about the i1DisplayPro. Granted the i1D2 was a POS from the start...
FWIW, if you haven't already, get into i1Profiler. It has a number of capabilities that have lead me to ditch the other options when it comes to "regular" display profiling (aside from displays with internal calibration hardware). For example it already has compensation profiles built-in for the i1DisplayPro for several types of display light sources.
Check it out, calibrate the same display with both devices and do some real world evaluative testing. I think you'll find either device will work surprisingly well...