Nice customised titlepage for every section (scrartcl)

Question

I have a relatively simple LaTeX document with a few sections and subsections and everything would be fine, BUT: I would like to have a custom designed titlepage for every section. (btw. MWE at the bottom!) My TOC looks like this:

Right now, the page with a new section (e.g. 2 A second...) looks like this:

But I rather would like to have something that stands out! This is my idea, how I would like to see e.g. section 2:

You find a MWE is below!

My question now is: How can I create these nice looking title pages for my sections? I think there are some possibilities with the titlesec package. But I'm not good in trying it myself. Can anybody help me with this? Any help is very much appreciated!

\documentclass[%
a4paper,
11pt,
headsepline,
footsepline,
]
{scrartcl}


\usepackage[english]{babel}
\usepackage[T1]{fontenc}
\usepackage[ansinew]{inputenc}
\usepackage{booktabs}                           
\usepackage{amsmath}                            
\usepackage{tabularx}
\usepackage{seqsplit}
\usepackage{longtable}                      
\usepackage{wrapfig}
\usepackage{ulem}                   
\usepackage[version=3,arrows=pgf]{mhchem}
\usepackage[pdf]{pstricks}
\usepackage{acronym}
\usepackage{wasysym}            
\usepackage{rsphrase}                       
\usepackage{siunitx}                        
\usepackage{tikz}                           
\usepackage{float}
\usepackage{geometry}
\geometry{bottom=3.5cm}
\geometry{top=3.5cm}
\geometry{left=2.5cm}
\geometry{right=2.5cm}
\usepackage{enumerate}                          
\usepackage{multirow}
\usepackage{lscape}
\usepackage{rotating}
\usepackage{subfigure}
\usepackage{url}
\usepackage{setspace}
\usepackage{threeparttable}
\usepackage{array} 
\usepackage{graphicx}
\usepackage[labelfont=bf,format=plain]{caption}
\usepackage[linkcolor=black,citecolor=black]{hyperref}
\makeatletter
\@addtoreset{figure}{section}
\@addtoreset{table}{section}
\makeatother 
\renewcommand{\thefigure}{\thesection.\arabic {figure}}
\renewcommand{\thetable}{\thesection.\arabic{table}}    

\newcolumntype{P}[1]{>{\raggedright\arraybackslash}p{#1}}
\setcounter{tocdepth}{3}   
\setcounter{secnumdepth}{3}  

\sisetup{%
    obeyall,            
    per=frac,               
    decimalsymbol=comma,    
    unitmode=text   
    }

\hbadness=10000
\vbadness=10000
\hyphenpenalty=100000
\definecolor{gray75}{gray}{0.75}
\newcommand{\hsp}{\hspace{20pt}}
\linespread{1.25}

\begin{document}
\sloppy
\thispagestyle{empty}

\LARGE
\vspace{0.5cm}

\begin{center} \LARGE 
\textbf{\LARGE XXXXXXXXXXXXXXXXXXXXXXXXXXXXX\\}
\textbf{\LARGE XXXXXXXXXXXXXXXXXXXXXXXXXXXXX\\}
\end{center}
\vspace{1.0cm}

\begin{center}
\Large
XXXXXXXXXXXXXXXXXXXXXXXXXXXXX\\
XXXXXXXXXXXXXXXXXXXXXXXXXXXXX\\
XXXXXXXXXXXXXXXXXXXXXXXXXXXXX\\
XXXXXXXXXXXXXXXXXXXXXXXXXXXXX\\
XXXXXXXXXXXXXXXXXXXXXXXXXXXXX\\
XXXXXXXXXXXXXXXXXXXXXXXXXXXXX\\
XXXXXXXXXXXXXXXXXXXXXXXXXXXXX\\
\end{center}
\vspace{1.0cm}

\begin{table}[!h]
\Large
\begin{tabular}{ll}
XXXXXXXXXXXXXXXXXXXXXXXXXXXXX & \\
XXXXXXXXXXXXXXXXXXXXXXXXXXXXX& \\
\end{tabular}
\normalsize
\end{table}

\vspace{0.5cm}
\begin{table}[!b]
\Large
\begin{tabular}{ll}
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXh\\
XXXXXXXXXXXXXXXXXXXXXXXXXXXXX\\
XXXXXXXXXXXXXXXXXXXXXXXXXXXXX\\
v & \\
\end{tabular}
\normalsize
\end{table}
\normalsize

\clearpage
\thispagestyle{empty}

\setcounter{page}{1}
\pagenumbering{Roman}

\clearpage
\thispagestyle{plain}

\section*{section X}
XXXXXXXXXXXXXXXXXXXXXXXXXXXXX \\

\large
\paragraph{XXXXXXXXXXXXXXXXXXXXXXXXXXXXX}

\clearpage  
\thispagestyle{empty}

\phantom{oben}
\phantom{oben}
\phantom{oben}
\phantom{oben}
\phantom{oben}
\phantom{oben}
\phantom{oben}
\phantom{oben}
\phantom{oben}

\begin{flushright} \LARGE 
\textbf{\LARGE It will be fine.\\}
\end{flushright}
\vspace{1.0cm}

\clearpage
\thispagestyle{plain}
\tableofcontents

\clearpage
\listoffigures
\addcontentsline{toc}{section}{List of Figures}

\clearpage
\listoftables
\addcontentsline{toc}{section}{List of Tables}
\clearpage

\clearpage
\section*{some other hidden chapter}
XXXXXXXXXXXXXXXXXXXXXXXXXXXX

\clearpage
\setcounter{page}{1}
\pagenumbering{arabic}
\section{A first very nice and fancy looking title}

XXXXXXXXXXXXXXXXXXXXXXXXXXXXX 

\subsection{subsectionn 1-1}
XXXXXXXXXXXXXXXXXXXXXXXXXXXXX 

\subsection{subsectionn 1-2}

XXXXXXXXXXXXXXXXXXXXXXXXXXXXX 

\subsubsection{subsubsection 1-2-1}

%%%%%%%%%%%%%%%%%%%%%%%%%%
\clearpage
\section{A second very nice and fancy looking title}

\subsection{subsection 2-1}

XXXXXXXXXXXXXXXXXXXXXXXXXXXXX  

\subsection{subsection 2-2}

\subsubsection{subsubsection 2-2-1}
XXXXXXXXXXXXXXXXXXXXXXXXXXXXX  

\subsubsection{subsubsection 2-2-1}

\subsection{subsection 2-3}

XXXXXXXXXXXXXXXXXXXXXXXXXXXXX  

%%%%%%%%%%%%%%%%%%%%%%%%%%
\clearpage
\section{A third very nice and fancy looking title}

\subsection{subsection 3-1}

XXXXXXXXXXXXXXXXXXXXXXXXXXXXX  

\subsection{subsection 3-2}

\subsubsection{subsubsection 3-2-1}
XXXXXXXXXXXXXXXXXXXXXXXXXXXXX  

\subsubsection{subsubsection 3-2-1}

\subsection{subsection 3-3}

XXXXXXXXXXXXXXXXXXXXXXXXXXXXX  

\end{document}

Answer 1

Here is a solution in which I patched the \section command to get the desired formatting. The additional data, i.e. the "Here comes a small text..." part in your example picture is gathered via \sectionpreamble right before issuing the \section command:

\sectionpreamble{%
  Lorem ipsum dolor sit amet, consetetur sadipscing elitr,
  sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua.
  At vero eos et accusam et justo duo dolores et ea rebum.
  Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
  Lorem ipsum dolor sit amet, consetetur sadipscing elitr,
  sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua.
  At vero eos et accusam et justo duo dolores et ea rebum.
  Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
}
\section{There will be a very long title here that spans lots and lots and lots and lots and lots of lines}

The complete code would be:

\documentclass{scrartcl}
\usepackage{graphicx}
\usepackage{xcolor}

\makeatletter
\newdimen\thesectionwdmax
\newdimen\sectiontitlewd
\AtBeginDocument{%
  \setbox0=\hbox{\scalebox{5}{99}}
  \thesectionwdmax\wd0
  \sectiontitlewd\dimexpr\textwidth-\thesectionwdmax-2.25cm\relax
}
\def\section{\par
   \addvspace{4ex}%
   \@afterindentfalse
   \secdef\@sec\@ssec}
\def\@sec[#1]#2{%
    \ifnum \c@secnumdepth>\m@ne
      \refstepcounter{section}%\@maybeasf%
       \addcontentsline{toc}{section}{\protect\numberline{\thesection}#1}%
    \else
      \addcontentsline{toc}{section}{#1}%
    \fi
    {\parindent\z@
     \raggedright
     \interlinepenalty \@M
     \thispagestyle{empty}
     \normalfont
     \setbox0=\vbox{\parbox{\sectiontitlewd}{\noindent\huge#2}}
     \sectfont
     \raisebox{-1em}{\parbox[c]{\thesectionwdmax}{\noindent\null\hfill\scalebox{5}{\thesection}}}
     \hspace{.25cm}
     \raisebox{1em}{\parbox[t][\dimexpr\ht0+\dp0\relax]{1em}{\leaders\vrule\vfill}}
     \hspace{1cm}
     \parbox[t]{\sectiontitlewd}{\noindent\huge#2}
     \vfill\printsectionpreamble\vfill
     \sectionmark{}\par}%
     \nobreak
    \@afterheading
    \clearpage}
\def\@ssec#1{%
    {\parindent\z@
     \raggedright
     \interlinepenalty \@M
     \thispagestyle{empty}
     \sectfont #1
     \vfill\printsectionpreamble\vfill
     \sectionmark{}\par}%
     \nobreak
     \vskip 3ex
    \@afterheading
    \clearpage}
\def\printsectionpreamble{%
  \ifx\currentsecpreamble\empty\else
    \colorbox{pink}{\parbox{\textwidth}{\normalfont\normalsize\currentsecpreamble}}\fi
  \let\currentsecpreamble\empty}
\def\sectionpreamble#1{\gdef\currentsecpreamble{#1}}
\makeatother

\begin{document}
\sectionpreamble{%
  Lorem ipsum dolor sit amet, consetetur sadipscing elitr,
  sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua.
  At vero eos et accusam et justo duo dolores et ea rebum.
  Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
  Lorem ipsum dolor sit amet, consetetur sadipscing elitr,
  sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua.
  At vero eos et accusam et justo duo dolores et ea rebum.
  Stet clita kasd gubergren, no sea takimata sanctus est Lorem ipsum dolor sit amet.
}
\section{There will be a very long title here that spans lots and lots and lots and lots and lots of lines}
%...
\end{document}

Answer 2

Here is a suggestion redefining the KOMA-Script command \sectionlinesformat:

\documentclass{scrartcl}
\usepackage{graphicx}
\usepackage{xcolor}

\newdimen\thesectionwdmax
\newdimen\sectiontitlewd
\AtBeginDocument{%
  \setbox0=\hbox{{\usekomafont{disposition}\usekomafont{section}\scalebox{2}{99}}}%
  \thesectionwdmax\wd0%
  \sectiontitlewd\dimexpr\textwidth-\thesectionwdmax-.75cm-1pt\relax
}

\renewcommand\sectionformat{\protect\scalebox{2}{\thesection}}
\addtokomafont{section}{\huge}

\makeatletter
\renewcommand\sectionlinesformat[4]{%
  \ifstr{#1}{section}
    {\ifstr{#3}{}
      {\@hangfrom{\hskip #2#3}{#4}}
      {%
        \begin{tabular}{@{}r@{\hspace{.25cm}\vrule width 1pt\hspace{.5cm}}l@{}}
        \parbox{\thesectionwdmax}{\centering#3}%
        &%
        {\parbox{\sectiontitlewd}{\raggedright#4}}%
        \end{tabular}%
      }%
    }
    {\@hangfrom{\hskip #2#3}{#4}}%
}

\newcommand\sectionpreamble[1]{{%
  \vfill
  \setlength\fboxsep{2em}%
  \colorbox{lightgray}{%
    \parbox{\dimexpr\linewidth-2\fboxsep-2\fboxrule\relax}
      {\raggedright #1}%
  }%
  \vfill
  \clearpage
}}
\makeatother

\usepackage{lipsum}
\begin{document}
\tableofcontents
\section{There will be a very long title here that spans lots and lots and lots and lots and lots of lines}
\lipsum[1]
\section{A short title}
\lipsum[2]

\clearpage
\section{There will be a very long title here that spans lots and lots and lots and lots and lots of lines}
\sectionpreamble{\lipsum[1]}
\lipsum[5-6]

\section{Another section}
\lipsum
\addsec{Unnumbered section}
More text ...
\end{document}