There are few constants that usually come together, $e/m$ also $h/e$. How are they decoupled? If the speed of light is "derived" as Wikipedia states how meter defined and time?
If the result of a measurement is i.e. $3.2 \pm 0.7$, what is 0.7? At which confidence level we know that the real result is inside of this interval?
If the metre is now defined as the distance light travels in vacuum in 1⁄299,792,458th of a second and the speed of light is accepted to be ...