\def\mycite{\dodoubleempty\domycite}
\def\defaultciterepeat{Ebenda}
\def\defaultciteprefix{Vgl. }
\def\defaultcitepage{S. }
\def\defaultcitechapter{Kap. }

\def\domycite[#1][#2]{%
  \ifsecondargument%
    \getparameters[MCP][prefix={\defaultciteprefix},page=,chapter=,suffix=,repeat=,#2]%
    \doinsertmycite[#1]{\MCPprefix}{%
      \doifnot{\MCPpage}{}{\ \defaultcitepage\MCPpage.}%
      \doifnot{\MCPchapter}{}{\ \defaultcitechapter\MCPchapter.}%
      \doifnot{\MCPsuffix}{}{\ \MCPsuffix}%
    }%
  \else%
    \doinsertmycite[#1]{\defaultciteprefix}{}%
  \fi%
}

\def\doinsertmycite[#1]#2#3{%
  \footnote{%
    \doifelse{\MCPrepeat}{yes}{\global\setvalue{mycitelast}{#1}}{\doif{\MCPrepeat}{no}{\global\setvalue{mycitelast}{}}}%
    #2\doifnot{#2}{}{\strut}%prefix
    \doifelse{\getvalue{mycitelast}}{#1}%
      {\doifelse{#2}{}%
        {\defaultciterepeat}%
        {\lowercase{\defaultciterepeat}}%If there's a prefix, lower-case the cite-repeat string
        .%
      }%
      {\doifelse{\getvalue{mycitepast #1}}{used}%
        {\bgroup%
         \getcitedata[title][#1] to \bibtitle%
         \getcitedata[arttitle][#1] to \bibarttitle%
         \cite[alternative=authoryear][#1]. {\it\bibtitle\bibarttitle}.%
         \egroup}%
        {\cite[alternative=data][#1]}%
      }%
    #3%suffix
    \global\setvalue{mycitelast}{#1}%
    \global\setvalue{mycitepast #1}{used}%
  }%
}

%Reset last citation on page break (which we check when placing footnotes)
\appendtoks
  \doifnoteonsamepageelse[footnote]{}{\global\setvalue{mycitelast}{}}
\to\everyinsidenoteinsert