Your absolutism is a bit silly. I don't think the Imperial system is good for anything beyond construction or cooking, but there's a reason it excels those areas. And it's exactly because it's more usable by humans in certain contexts (like construction or cooking). 1/3 of a meter should not be an irrational number - how is that "optimized for humans"?
A scalable system that shares the divisibility of the foot would certainly trump both systems.
Base-10 absolutism rears its head again. The objection to 1/3 is that it has a non-terminating decimal expansion. This is not a problem if you're using base-anything-with-3-as-a-factor.
What about 1/5 instead? There's always going to be problems with some base, the point is that unit conversions are super easy with metric, and it's easier to teach to children.
As for temperature, 0 is really gold and 100 is really hot in pretty much every scale, that's just a very subjective way of describing things.
Uh, no. The final 2x4 product is milled mostly dry. Mills allow the timber to air dry, then mill, then post-kiln, and may mill the final product after that e.g. by cutting 2x4s out of a 12x4. The reduction of a 2x4 from 2x4" to 1.75x3.5" is done on purpose, because modern mills can put guarantees on the density of knots in the wood, thus requiring less wood for the same engineered strength guarantee. So the 2x4" product is not actually 2x4 because the mill is asserting that while there is less wood than just cutting a 2x4, the board they're selling is as strong as a 2x4 would have been at the turn of the 20th century, when they didn't have a way to guarantee the density of knots.
Math isn't intuitive for humans. It takes a lot of work to learn it and most people don't remember any of it past school age. If we taught base 12 instead of 10 it would be just as intuitive.
A scalable system that shares the divisibility of the foot would certainly trump both systems.