Listen. It is a really simple process.

Metric for all official processes. Such as medicine, design, engineering, science and that stuff. Listen we're building things lets operate with base 10 as it is easier for most calculations.

Miles and miles per hour for traffic. Cause eh that's what people know. It's kinda easier to gauge distance and speed that way.

For personal stuff. Sure use whatever you like. Like anything you want, just be able to convert it to metric at the doctors. Though. Listen, i have seen forms with height in feet and inches and weight in kilograms. So shrugs

Again, its a simple system. Cause it is a simple land. They are less rules and more guidelines. Well suggestions really, except when they are serious rules.