Your idea is self-consistent and mathematically sound, but it's based on false postulates that don't match reality. Experiments such as the Michelson-Morley experiment used very similar reasoning to yours in an attempt to detect the velocity of Earth's motion through "space", and found absolutely nothing regardless of countless improvements and repeat measurements all over the Earth at different times of year (and Michelson's original experiment was already incredibly precise as is). The rotation of the Earth, it's orbit around the sun... none of it made any difference, and their equipment was extremely delicately calibrated to notice even tiny motions. Are you at all familiar with this experiment?
Your concept of metres and seconds is historically backward. When the metre was originally defined, Relativity didn't yet exist. They made an extremely straight stick and took it to be the calibration standard, from which multiple copies were made, and multiple more copies from those, and so on, so everyone could use the same standard of measure. A similar procedure was undertaken to define a universal standard of 1 second, based on an extremely precise clock. That was when the SI system was originally founded.
Then people started going out and making precision measurements of the speed of light using their calibrated measurement tools, and they found that in vacuum they always got the exact same result, no matter how the detector or the source were moving. That was also a requirement of classical electromagnetism, which demands the introduction of Relativity in order to apply in a self-consistent fashion in all inertial frames. Then along came Einstein to explain all the weird results people were getting, using Relativity. Now we know that certain radioactive decays give off the exact same frequency of light anywhere in the universe, and we can use that to define units of 1 second in such a way that anyone could construct their own accurate clock without copying the standardized one in Paris. And knowing as we now do that any observer measures the exact same speed for light no matter how they move or how the source moves, we can use it to define a metre in such a way that anyone in the universe could construct a metre stick exactly matching the one in Paris without needing to ever travel there.