I tried playing this mod instead of mineral processing but when I got to a certain point I ended up becoming very frustrated due to steel production, In a normal game steel production is bottle necked by a few factors one of which is lime and lime is itself bottle necked by it being a secondary product that has to be refined from hard to get minerals or animal products. This makes steel difficult without some time investment in ranching,

By changing the steel recipe to borax you create a three prong issue.

• If you are willing to crush salt for borax (not that you have a choice as it's the only source) you completely remove one of the bottle necks of steel making it ridiculously easier to create until your salt runs out.
  
  
• Salt is much harder to replace than the sources for lime as the two methods that give you salt you may not have easy access too by random chance and both require a further process to get the salt from that resource those being dasha vines and the desalinator.
  
  
• In any start where you have a great deal of rust you usually have a lack of polluted mud and/or algae meaning you rely on the salt for oxygen production making it very problematic to crush it to get borax.

All of these problem could be addressed by another method of procuring borax not directly tied to destroying salt.

After reading about borax if you want something that is somewhat relevant to how borax naturally occurs (occurring where there's seasonal evaporation) I would suggest making it so the desalinator creates a small amount of borax as well as salt.

Another option is that borax can be synthesized from other boron compounds which don't exist in the game but a boron compound is zinc borate so you could add a recipe in the molecular forge to make borax from zinc and some other material.

Edit:

After some reading another thing that has boron in it is Borosilicate glass, so perhaps crushing glass might yield sand and some borax.