Déplacer des colonnes dans un tableau

\documentclass{article}
\usepackage{spreadtab,array,booktabs,tabularx}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\makeatletter
\long\def\MT@get@body@env#1\end{\ST@add@tomacro\ST@tab{#1}\MT@find@end}

\newcommand*\MT@find@end[1]{%
    \def\ST@temp@a{#1}%
    \ifx\ST@temp@a\MT@envname
        \expandafter\movetab@i
    \else
        \ST@add@tomacro\ST@tab{\end{#1}}%
        \expandafter\MT@get@body@env
    \fi
}

\def\movetab#1\begin#2#3{%
    \begingroup
        \def\MT@envname{#2}%
        \expandarg\noexploregroups
        \def\MT@tab@preamble{\begin{#2}{#3}}%
        \def\MT@tab@end{\end{#2}}%
        \def\MT@optcode{#1}%
        \let\ST@tab\@empty
        \MT@get@body@env
}

\def\movextab#1\begin#2#3#4{%
    \begingroup
        \def\MT@envname{#2}%
        \expandarg\noexploregroups
        \def\MT@tab@preamble{\begin{#2}{#3}{#4}}%
        \def\MT@tab@end{\end{#2}}%
        \def\MT@optcode{#1}%
        \let\ST@tab\@empty
        \MT@get@body@env
}

\newcommand*\movetab@i{%
        \MT@read@tab
        \MT@genlistcol
        \unless\ifx\MT@optcode\@empty\expandafter\MT@movecol\MT@optcode,\relax->\relax,\fi
        \let\ST@tab\MT@tab@preamble
        \MT@build@tab
        \ST@expadd@tomacro\ST@tab\MT@tab@end
        \ST@tab
        \restoreexpandmode\restoreexploremode
    \endgroup
}

\newcommand*\MT@read@tab{%
    \def\ST@total@colnumber{0}%
    \ST@rowcount\z@
    \ST@search@hline
    \MT@read@tab@i
}

\newcommand*\MT@read@tab@i{%
    \advance\ST@rowcount\@ne
    \ST@Ifinstr\ST@tab{\ST@eol}%
        {\expandafter\ST@split\expandafter\ST@tab\expandafter{\ST@eol}\ST@current@row\ST@tab
        \@namedef{endrow@\number\ST@rowcount\expandafter}\expandafter{\ST@eol}%
        \ST@Iffirstis\ST@tab[%
            {\ST@between\ST@tab[]\ST@temp@a
            \ST@Ifinstr\ST@temp@a,%
                \relax
                {\ST@split\ST@tab]\ST@temp@a\ST@tab
                \expandafter\ST@expadd@tomacro\csname endrow@\number\ST@rowcount\endcsname{\ST@temp@a]}%
                }%
            }%
            \relax
        \ST@search@hline
        \ifx\ST@tab\@empty
            \let\ST@next@readrows\relax
            \edef\ST@total@rownumber{\number\ST@rowcount}%
        \else
            \let\ST@next@readrows\MT@read@tab@i
        \fi
        }%
        {\let\ST@current@row\ST@tab
        \let\ST@next@readrows\relax
        \edef\ST@total@rownumber{\number\ST@rowcount}%
        }%
    \ST@colcount\z@
    \MT@read@cells
    \ST@next@readrows
}

\newcommand*\MT@read@cells{%
    \advance\ST@colcount\@ne
    \ST@Ifinstr\ST@current@row&%
        {\ST@split\ST@current@row&\ST@current@cell\ST@current@row
        \let\ST@next@readcells\MT@read@cells
        }%
        {\let\ST@current@cell\ST@current@row
        \let\ST@next@readcells\relax
        \ifnum\ST@colcount>\ST@total@colnumber\edef\ST@total@colnumber{\number\ST@colcount}\fi
        }%
    \ST@letname{text@\number\ST@colcount @\number\ST@rowcount}\ST@current@cell
    \ST@next@readcells
}

\newcommand*\MT@genlistcol{%
    \ST@colcount\z@
    \def\MT@listcol{,}%
    \loop
        \advance\ST@colcount\@ne
        \unless\ifnum\ST@colcount>\ST@total@colnumber\space
        \edef\MT@listcol{\MT@listcol\number\ST@colcount,}%
    \repeat
}

\def\sanitize@listcol,#1,\@nil{\def\MT@listcol{#1}}

\def\MT@movecol#1->#2,{%
    \unless\ifx\relax#1%
        \StrBetween[\numexpr#1,\numexpr#1+1]\MT@listcol,,[\ST@temp@a]%
        \StrSubstitute\MT@listcol{\expandafter,\ST@temp@a,},[\MT@listcol]%
        \StrCut[\numexpr#2]\MT@listcol,\MT@listcol\ST@temp@b
        \edef\MT@listcol{\MT@listcol,\ST@temp@a,\ST@temp@b}%
        \expandafter\MT@movecol
    \fi
}

\newcommand\MT@build@tab{%
    \expandafter\sanitize@listcol\MT@listcol\@nil
    \ST@rowcount\@ne
    \expandafter\ST@expadd@tomacro\expandafter\ST@tab\csname endrow@0\endcsname
    \MT@build@tab@i
}

\newcommand\MT@build@tab@i{%
    \ST@colcount\@ne
    \@for\MT@colnum:=\MT@listcol\do{%
        \ifcsname text@\MT@colnum @\number\ST@rowcount\endcsname
            \expandafter\ST@expadd@tomacro\expandafter\ST@tab\csname text@\MT@colnum @\number\ST@rowcount\endcsname
        \fi
        \advance\ST@colcount\@ne
        \unless\ifnum\ST@colcount>\ST@total@colnumber\relax\ST@add@tomacro\ST@tab&\fi
    }%
    \ifcsname endrow@\number\ST@rowcount\endcsname
        \expandafter\ST@expadd@tomacro\expandafter\ST@tab\csname endrow@\number\ST@rowcount\endcsname
    \fi
    \advance\ST@rowcount\@ne
    \unless\ifnum\ST@rowcount>\ST@total@rownumber
        \expandafter\MT@build@tab@i
    \fi
}

\makeatother
\begin{document}
\parindent=0pt
Essai 1 : colonne 1->3

\movetab 1->3
\begin{tabular}{ccc}\hline
    foo & bar        & BAZ \\[2ex]
    123 & 456        & 789 \\
    a   & \textbf{b} & c   \\\hline
\end{tabular}

\vskip2cm

Essai 2 : échange des colonnes 1 et 5

\movetab 1->5,4->1% échange les colonnes 1 et 5
\begin{tabular}{|*6{>{\centering\arraybackslash}m{1cm}|}}\hline\hline
     1 & 2 & 3 & 4 & 5 & 6\\
     a & b & c & d & e & f\\\cline{1-4}
     11& 22& 33& 44& 55&66\\\noalign{\vskip1ex}
     A & B & C & D & E & F\\\hline\hline
\end{tabular}

\vskip2cm

Essai 3 : colonne 2->3, 4->5 et 6->1

\movetab 2->3,4->5,6->1
\begin{tabular}{*6{c}}\toprule[1.5pt]
     1 & 2 & 3 & 4 & 5 & 6\\\midrule[0.5pt]
     a & b & c & d & e & f\\
     11& 22& 33& 44& 55&66\\
     A & B & C & D & E & F\\\bottomrule
\end{tabular}

\vskip2cm

Essai 4, tabularx : colonne 1->4

\hfill
\movextab 1->4
\begin{tabularx}{0.75\linewidth}{|c|c|c|X|}\hline
    1 & 2 & 3 & 4\\
    11111111111111111 & 222222 & 3333 & 44\\\hline
\end{tabularx}
\hfill\null

\end{document}