(OOP here). I wonder if switching my replies from 299 to 200 OK would be enough for some of them.

Unlikely, but the lazy wonks could enable stratum 1 time services with the cars GPS/cellular receiver and RTC. Having done that for equipment in the past, we all know it is literary only $8.43/unit in parts. Also, setting ntp time as the tertiary fall back has been around for over a decade. =3