Before you go on about what VHDL will and will not do ,that you get yourself a good book on the subject.
If you want to use a decimal constant to define a divider then
you can go;-

constant DIV1: integer:=112 -- which is pretty decimal

variable Clock_Divisor : integer range 0 to 600 ;

begin
if (Local_Reset = '1') then
Clock_Divisor := 0 ;
Rate_Clock_X16 <= '0' ;

elsif (rising_edge(clock)) then
Clock_Divisor := Clock_Divisor + 1 ;
Rate_Clock_X16 <= '0' ; -- Inertial assignment
if (Rate_Select = '0') then -- Low speed
if (Clock_Divisor = DIV2) then
Clock_Divisor := 0 ;
Rate_Clock_X16 <= '1' ;
end if ;
else -- High speed
if (Clock_Divisor = DIV1) then
Clock_Divisor := 0 ;
Rate_Clock_X16 <= '1' ;
end if ;
end if ;

end if ;
end process ;

Sorry if its not formatted but I cannot be bothered and i don't feel like teaching the ins and outs of a language to somebody who comes along with a load of preconceived ideas about what it will and won't do.