You would buy your leather from a tannery, laces would be split then cut on a lace cutter, no certification required,the tumbling machine is normally just a drum with baffles in it, the machinery would be subject to your factory and production, re doing it at home or industrial site.
Employees would be governed by the size of your business and how much capital you have.
This is a veg tan process but chrome tanning is the similar but uses different chemicals.
http://www.hermannoa...nery-tour-video
You will need to know how to dispose of these chemicals which could be a big expense.
Kevin