They would charter an aircraft and pilot from an AOC operator.
No, they would not fly at all because without the yacht related business that I generate there would be no need for the travel. My company certainly would not pay for a "professional pilot" who has no productive use outside of the cockpit.
You may be right that it is illegal (I am making further enquiries) but if it is, it is not a good regulation. The regulation is the equivalent of forcing every businessman to travel only in licenced taxis and preventing them from driving themselves on business. Business would clearly suffer for no advantage and that is not good for anybody.