Beamer theme: customizing title page

Question

I usually use the default theme of beamer for its simplicity.

I want to change the titlepage of default theme to the one like the titlepage of metropolis but with

1. the line with default color of default theme; and
2. white background color like this:

I tried the following code which uses the answer in Customizing beamer title page? :

\documentclass[10pt, xcolor=table, handout, notheorems]{beamer} 
\usepackage{tikz}
\usetheme[]{default}

\makeatletter
\setbeamertemplate{title page}{
  \vbox{}
  \vfill
  \begingroup
    \centering
    \begin{beamercolorbox}[sep=8pt,center]{title}
      \usebeamerfont{title}\inserttitle\par%
      \ifx\insertsubtitle\@empty%
      \else%
        \vskip0.25em%
        {\usebeamerfont{subtitle}\usebeamercolor[fg]{subtitle}\insertsubtitle\par}%
      \fi%     
    \end{beamercolorbox}%
    \vskip1em\par
    \begin{beamercolorbox}[sep=0.35cm,wd=\the\@tempdima]{frametitle}
       \begin{tikzpicture}
        \draw[line width = 1.5] (-2,0) -- (12,0);
       \end{tikzpicture}
    \end{beamercolorbox}
    \begin{beamercolorbox}[sep=8pt,center]{author}
      \usebeamerfont{author}\insertauthor
    \end{beamercolorbox}
    \begin{beamercolorbox}[sep=8pt,center]{institute}
      \usebeamerfont{institute}\insertinstitute
    \end{beamercolorbox}
    % ------------------------
    \begin{beamercolorbox}[sep=8pt,center]{date}
      \usebeamerfont{date}\insertdate
    \end{beamercolorbox}\vskip0.5em
    {\usebeamercolor[fg]{titlegraphic}\inserttitlegraphic\par}
  \endgroup
  \vfill
}
\makeatother

\title{bbbbbbbbb}
\author{aaaaaaaa}
\institute[]{ABC University}
\date{\today}

\begin{document}
\frame{\titlepage}
\end{document}

Answer 1

The following approach (apart from the font) could be a good starting point. I tried to keep the things as simple as possible.

Code

\documentclass[10pt,xcolor=dvipsnames]{beamer}
\usepackage{kerkis}
\usepackage{kmath}
\usecolortheme[named=Blue]{structure}
\setbeamerfont{title}{series=\bfseries}
\setbeamerfont{author}{size=\normalsize}
\setbeamercolor{author}{fg=structure.fg}
\setbeamerfont{date}{size=\small}
\setbeamercolor{date}{fg=structure.fg}
\setbeamerfont{institute}{size=\small}
\setbeamercolor{institute}{fg=structure.fg}
\setbeamertemplate{title page}{%
    {%
    \usebeamercolor[fg]{title}
    \usebeamerfont{title}
        \MakeUppercase\inserttitle
    }
    \par\medskip
{%
\color{Blue!30!cyan}
    \rule{\linewidth}{1pt}
}
\par\medskip

{%
\usebeamercolor[fg]{author}
\usebeamerfont{author}
    \insertauthor
}\par\smallskip

{%
\usebeamercolor[fg]{date}
\usebeamerfont{date}
    \insertdate
}\par
{%
\usebeamercolor[fg]{institute}
\usebeamerfont{institute}
    \insertinstitute
}

}
\title{Title of the talk}
\author{Some Author}
\institute[]{ABC University}
\date{\today}
\begin{document}
\maketitle
% \begin{frame}{My frame}
% Some text
% \end{frame}
\end{document}

Output