The TPS64203 based design will not have enough gate drive to drive that kind of power out of any FET, esp the PFET that is required for this type of design. I suggest you look at the link below for similar reference design that our design services team has already built and tested.
http://www.ti.com/lsds/ti/analog/powermanagement/power_portal.page
then scroll down to PowerLab.
