Creating a standardized metric system solely to ensure that your constructed dollhouses are perfectly proportioned is like single-handedly destroying big tobacco just because you don’t want to smell secondhand smoke
Also, gotta wonder how they set up their measurement specifications. In our world it’s all based on immutable laws - the meter is how long a beam of light travels in a fraction of a fraction of a second, for instance. It used to be based off standard measurements, but even with those you can get deviations after a while.
I think you would still have to start with standard measures, like the kilogram blocks, until you establish the proper universal constants and their relations, along with precise enough instruments to perform your measurements.
How would a 16th century scientist/engineer construct the first 1 kg reference block from the current universal constants? How do I get a 1 cm mark on ruler? If we don't have it, it becomes impractical to standardize measurement in industry.
The way I see it is that current constant definition is really great at securing the basis for reference weights that can be reconstructed "anywhere", but it relies heavily on the fact we are capable of extremely precise measurements. A reference weight must still be made in order to derive all other weights used in industry.
In short, in order to convert our constant based definitions for measurements into practical everyday applications, a solid scientific theory is needed, which is not available to 17th century scientists. Hence, start as we did. Once you have the theory, just define the constants so that they match the previous units. That is what we did.