I seem to recall that FDR tried exactly that, and it was determined that it was a bad plan overall...
Seem to recall FDR changed the ballance of th eCOurt from
37-41-appointing Black(from the KKK),Reed,Frankfurter(an
ACLU /Commie symp) douglas ,Murphy ,Byrnes,and Jackson.and YES it was a very bad idea- one whose consequesnses we have not recovered from.