We appreciate that you are giving us this suggestion. I'll be sure to share those with the rest of the team for consideration.
Unfortunately, switching from hourly to fixed-price contract is not possible. If you and your freelancer would like to go from an hourly to a fixed-price contract, simply end the hourly job and rehire the freelancer, changing the offer terms to a fixed-price contract. If do so, please discuss the new payment terms with your freelancer beforehand to avoid any inconveniences.