I ran my own very, very successful business for 40 years so I'm quite confident that I am clued up enough to comment how businesses work. Have you ever run a business ?
As I said all roles are important to the running of any business but my answer was to which role was the most important.
Remove those that do the invoicing, wages, cleaning etc. Those that produce the product that generates the revenue could still send out the invoices, do the wages, clean the office and workshop. It might make the day longer but it would still get done.
Keep those that do the invoices, do the wages and clean the office and get rid of the revenue producers and those left have nothing to invoice, no wages to pay, apart from their own but there won't be any money to pay them as nothing is being produced and sold.