So, I played a bit around with your mod.

One thing in particular that is kind of annoying me.
You get the same amount of items from any recipe, no matter how advanced the origin material is.
Why would one ever use the steel > gear recipe when the iron > gear has the exact same yield?
Shouldn't higher origin materials have a bigger yield?

This I imagine will be later balanced down as recipes become higher tier, likely by requiring x girders such that Y property reaches say total 540.

Plus you might be able to then alter the pipe underground length based on how much Z property it has too, this can be done for assemblers (a material might have higher conductivity, so does the assembler run at a higher speed, dependent on the torque capability of the titanium gears), and interestingly for modules....

Right now, that's unfortunately how it is. My hope is, when 2.0 comes out, to have better materials yield better quality machined parts, but we're not there yet. I've also got other ideas for how to differentiate them. But, nothing concrete yet.

This I imagine will be later balanced down as recipes become higher tier, likely by requiring x girders such that Y property reaches say total 540.

Plus you might be able to then alter the pipe underground length based on how much Z property it has too, this can be done for assemblers (a material might have higher conductivity, so does the assembler run at a higher speed, dependent on the torque capability of the titanium gears), and interestingly for modules....

This would mean creating a new version of each assembler for each different possible set of values of properties which apply to the assembler. This would likely be like the amount of ingredients squared assemblers. The recipe would be slightly different for each one, and you might want to tweak the behaviour of assemblers to allow hiding certain recipes in the crafting menu (because there wouldn't be one). This would pretty much break the game in it's current state though, but it is a good idea.