It’s already defined that way - from Wikipedia "From 1983 until 2019, the metre was formally defined as the length of the path travelled by light in a vacuum in 1/299792458 of a second. After the 2019 redefinition of the SI base units, this definition was rephrased to include the definition of a second in terms of the caesium frequency ΔνCs. "
Just because it’s defined as some section of a light year does not mean it’s using a light year as a reference. You could use a foot and find the fraction of a light year that represents it, but that doesn’t mean that the foot is based on a light year.
I’m saying the short measure that we use on a daily basis might be a BASE 10 portion of a light year. Not 1/299792458 of a light second.
P.S. It’s like being on Reddit, being download for conjecturing.
I see what you mean. That is just as arbitrary as using the Earth’s size or any other reference. There’s nothing special about a year.