The XCR platform is unique to say the least, when I was doing my research back in the day to purchase a 5.56 type semi and decided on the XCR-L, it was because of the multiple caliber options and the cost of the kits. Back then I think RA was the only company that actually had a rifle that offered those options. The accuracy was as good as the ARs from what I saw back then. The piston driven, side charging, ambi-magazine release and the ambi-safety (which came later on) are all positives for me.
Keep in mind that I am no operator like yourself but that same things you are saying you like about the XCR is why most of us have stuck with RA. Which as you probably already know that Alex can be a little eccentric about his baby. I can say though that the QC and CS has improved immensely over the years. This drove Francis RIP (SDDUC996) away initially but he believed in the platform and I believe if he was still with us, I would like to think he would have come back. I think he worked closely with the 'Teams' while he was active duty.
Kermit, Navalbeaver or Mechanic would be my recommended contacts for products if you decide to adopt the XCR. NB and Mech has posted several details about the rifles.
M-LOK might be a reach for Alex to adopt, long story, there are some feelings there from the RA side.
Got to add, the XCRs are super easy to clean, not that some of our members do so on a regular basis.