I don't have a good answer for you, as your points are valid. It could just have easily been above my G5. I have always thought about it as a device I don't need to access except for testing (or failure) so I wanted it out of prime real estate. Perhaps I'm victim to bias (many other panels including the RV-6A I'm currently flying have it on the far right). Or maybe it's because it is the most dated item on the panel (not been updated, not very ergonomically/esthetically designed as it is either very recessed as I have it mounted or very protruding if front mounted) and I don't want to look at it. Or maybe I naively believe it will never be used (passively or actively).
I can say that the only time I have used one was in my RV-6A when it went off by mechanical fault, I knew it through my headset, and we flew with my passenger pressing the reset button continuously for 25 minutes to silence it until we landed and disabled it. In that case, I was glad it was on the passenger side, but that's a pretty unusual case.
No good answer for you. ( I am okay with the CO detector on the far right as I have it connected to the G3X).
RV-14A Builder - kit #136
N314KC - First flight Mar 8, 2017, >300 hrs
Sport Pilot (weight-shift control) - Airborne XT912
Dues paid 11/2017