The P10 is returned! Here's the after-action report, in hopes it might help others.
I bought this pistol used on the local market, face-to-face. About the time I was ready to have Primary Machine or whomever add the anti-rotation slot and striker cage to my early-version P10, the service was removed from their site and I couldn't find another vendor who'd provide the machining.
I sought advice here, and as y'all can see BG above suggested I just contact CZ-USA. Since I'm not the original owner I didn't think of this myself, but to my surprise, they just said "yeah, here's a label, send it in."
The process took about 5 weeks, and I got a weekly email updating the status of the job. All said and done, it's back, the work is done, and according to them it function-fired just fine. Not sure when I'll get to the range myself but I anticipate no issues.
I'm pretty pleased overall, so thanks to BG who recommended the action. Oh - and the whole operation was at no cost to me, as well.
Now, if I can just find a P10F upper to long-slide it when I want...