What happens when you pay them at 7pm on a Friday and they try to cash out on Saturday at 10am, only to discover that their $1600 is now $1200? You're going to lose that employee and the Department of Labor will fine the shit out of you.
That's considering the dip in price at weekends.
What if he bought $1600 worth of coins on a Saturday / Sunday, then paid his employee(s) on the Monday or Tuesday?
With the dip on the weekend taken into account, the coins should be worth slightly more by mid week, so when he pays out $1600 of coins to the employee(s) he may have a little change left for the next week of wages.
On the other hand, if the employee has agreed to accept bitcoin as payment, surely they should be fully aware that the price could go either way after they're paid.