Method boils down to, no till, plant a mix of cover crops, and don't plant mono culture. Ended up getting a inch of top soil a year.
You're starting halfway on the track. Most things you plant in arid soil won't grow, which is the situation where the GP started from. Sure, once you have a soil quality where your crop mix grows, it will take less than 50 years.
"How to get an inch of topsoil?" - "first, have an inch of topsoil" isn't really the scenario the GP was thinking of.
Or, crazy idea, just do exactly what we do with fertilizer. Identify what's missing, prepare it en masse, and add it back in. This could include microbes, minerals, certain types of organic material, you name it. As our understanding of a system improves so too does our ability to efficiently manipulate it to achieve the end result that we want.
For the record, I believe you drastically underestimate our current practices and capabilities. We've been performing nitrogen fixation on an industrial scale since the early 1900s.
Its not about capabilities, ita about cost.
Growing alfalfa would help, but that is often not that profitable compared to reaping the soil and throwing on more artificial fertilizer until the soil is garbage.