It’s a robust rule I’d like to see implemented. Obviously there’s a lot of nuance and important details, some if which you highlighted, but the general idea is, that the goal should be to make a policy that’s “fair” in some way or another, and not just go “hur dur muh free trade” free-for-all. For example, I’d probably give Mongolia a bit of leeway as it’s a poor, developing nation to help them catch up, whereas I think US should be punished mot for the reasons you highlight, but for being a tax haven and maybe even for pollution.

But in general, my argument isn’t about some specific countries, but instead about specific products. A company in Mongolia selling to EU could either not give their employees medical insurance and sell widgets to EU for €50 + 100% tariffs, or treat their employees by EU standards and sell widgets for €100 and no tariffs. The ideal tariffs would exactly balance that (while still allowing Mongolian widgets to be cheaper because of lower wages because of lower cost of living.)