Yeah, if you ignore the ratios, "NaCHO" represents every sodium salt of an organic compound containing only carbon, hydrogen, and oxygen. There are many of these compounds:
I see what you mean but did you in fact try to push the ratio of Béchamel and cheese in a Mornay to the limit? I got pretty satisfying results that way.
And you can make sodium citrate at home with 4.9 grams of baking soda and 3.7 grams of citric acid. Add about 15 ml of water to start the reaction and wait. The cool thing about this reaction is that there shouldn't be any side products beyond some co2 and a little water.
Anyway, you'll get about 5 grams of sodium citrate dissolved in water. (and you can safely boil off the water to get pure sodium citrate powder)
Which is far more than you need to make a pot of melty goodness.
Now, you could just make a béchamel and slowly melt a young cheese into it, but that's never going to taste the same. Sodium citrate adds in just a little extra tartness, while also making the cheese so creamy that it's kind of hard to describe for those who've not had it.
I am not a fan of highly processed, salt melted cheese in general but the technique you´re describing is very interesting for homemade cheese sauces made from quality cheese. However, I was under the impression that american cheese sauces often contain at least a part if not all fake cheese.