Any officer or agency head may—

(1) appoint civilian personnel without regard to section 5331(b) of title 5 and without regard to the provisions of title 5 governing appointments in the competitive service; and

(2) fix the rate of basic pay for such personnel without regard to the provisions of chapter 51 and subchapter III of chapter 53 of title 5 relating to classification and General Schedule pay rates,

except that no individual so appointed may receive pay in excess of the annual rate of basic pay payable for GS-18 of the General Schedule, as the President deems appropriate to carry out this chapter.