What I'd like to see is a ruler with very thin markings. Someone should research (or look up) just how thin a marking can be while staying visible. And figure out what colors are best for this purpose. Maybe flurescent, or even back-lighted.
While I'd like everything to be metric, the physicist's point of view is that when a conversion is linear, be grateful, it's simple enough. If it's a calculation you often have to do, get a calculator like an accountant, or a scale or table.
For more info on definitions, see:
https://www.nist.gov/pml/weights-and-measures/si-units-length
"In 1958, a conference of English-speaking nations agreed to unify their standards of length and mass, and define them in terms of metric measures. The American yard was shortened and the imperial yard was lengthened as a result. The new conversion factors were announced in 1959 in Federal Register Notice 59-5442 (June 30, 1959), which states the definition of a standard inch: The value for the inch, derived from the value of the Yard effective July 1, 1959, is exactly equivalent to 25.4 mm."
So nowadays, it's the inch that's defined in terms of a fraction of a meter. The meter is defined in terms of the speed of light, and the wavelength of a photon emitted by a cesium atom going from 1 ground state to another (it has 2 ground states). Those are things that could be measured anywhere, not just on Earth.