I think that you will lose a large number of potential buyers of your products. . Thus, you can use the sale of your products for altcoins as an additional payment method, and not as the main one.
Depends on what altcoin he is talkin about. If it's a foreign one then yes but if it's a popular one, not really. Also it depends on the quality of his product. If it's superb, people will always try their best no matter how difficult it is, only to get it.
I still like your suggestion there of using only the alts as additional, so that he can maximize his sale or customer reach, as we believed that some people still prefer the traditional payment methods such as fiat, bank cards, and the likes. It might take some time before all of us transition to the cryptos and other digital forms of payment methods.
Your task as a business owner is to create convenient payment methods that would be available to every customer, and not create a problem for him
If his business is about payment methods, yes but he said his business is about cosmetic products.