File multipage with variable page format

I'm afraid you have to come up with your own solution for your problem.

The standalone style in combination with TikZ will produce a single PDF-page for each tikzpicture having the size of the (TikZ-)picture. Maybe this could be a start for you. You could include your figures using node and includegraphics.

This code will generate a PDF with three pages (just filled with a coloured rectangle).

documentclass[tikz,crop=true,border=-3pt]{standalone}
begin{document}

begin{tikzpicture}
fill[red] (0,0) rectangle (2,3);
end{tikzpicture}

begin{tikzpicture}
fill[green] (0,0) rectangle (5,5);
end{tikzpicture}

begin{tikzpicture}
fill[blue] (0,0) rectangle (3,1);
end{tikzpicture}

end{document}

You could use the adjustwidth environment from the changepage package.

...
usepackage{changepage}
...
begin{adjustwith}{}{-8em}
wider text
end{adjustwidth}
...

The two arguments lengths are added to the left and right margins respectively; positive value(s) decrease the local textwidth and negative value(s) increases it.