Recording and replaying PEC is a great idea, but, in reality for a mount like a synscan (we have 3 of them), there are issues you need to consider.
The periodic error comes from many sources. First source is the gear on the motor, which meshes with another gear, with finally meshes with the gears on the RA axis. The result is complex curve that has the sum of 3 different periods overlapped with each other, one has a period of a few seconds, one a few minutes, and one 24 hours. To get it 'right' to the point of knowing how it will behave over a full evening of tracking, you really have to spend a whole night measuring. Then, release the clutch, make an adjustment on the telescope, and re-tighten the clutch, things are no longer in sync. Now you have to start over measuring things.
The reality is, in my opinion, trying to correct for PE on these mounts without any feedback at all, is indeed worse than nothing. You are essentially steering blind making corrections for errors that you may or may not have correctly identified, and will often end up just making things worse, and even if not worse, not nearly as good as you want them to be.
I have done plots for the EQ6, and here is the end result. Blue line is unguided data where I did a full plate solution on every image from the guide camera to get a fairly good measurement on the periodic error. I was experimenting with guiding algorithms at the time, and the orange line is the result after guide corrections were applied, and I dont remember offhand which methodology this graph was for. The important detail to take away from that graph, periodic error is periodic, but, it's NOT smooth and it's not a nice sine wave like a lot of folks seem to think. In some parts of the curve it's a relatively slow movement, and in others it's a much faster movement.