How can I cange the fontsize mid document to have the same effect locally as setting the fontsize in the documentclass globally.
Consider the following minimal example:
\documentclass[a4paper,12pt]{article}
\pagestyle{empty}
\begin{document}
\section*{Text in 12pt}
Some text
\footnotesize footnotesize
\small small
\normalsize normalsize
\large large
\newlength{\FSize}
\setlength{\FSize}{10pt}
\newlength{\Baselineskip}
\setlength{\Baselineskip}{1.2\FSize} % Compare http://tex.stackexchange.com/a/94385/4011
\section*{Text in 10pt}
\fontsize{\FSize}{\Baselineskip}\selectfont
Some text
\footnotesize footnotesize
\small small
\normalsize normalsize
\large large
\end{document}
This gives the following output

As you can see, this is not what I wanted, setting the font size this way locally it doesn't have locally the same effect as correspeondingly setting the fontsize in the option of the documentclass globally. For example commands like \section or \small are not changed (but if I change the font in the documentclass they do change).
So is there an easy way to achieve this?

relsizepackage (http://www.ctan.org/pkg/relsize) be a first approach? – Ruben Oct 29 '14 at 18:10