次のソースをbbl.luaとでもして保存．

kpse.set_program_name("texlua")
if arg[1] == nil then
    print("no input")
    os.exit(1)
end

local file = arg[1]
if file:sub(-4,-1):lower() ~= ".bbl" then file = file .. ".bbl" end
file = kpse.find_file(file)
if file == nil then print("error: file not found") os.exit(1) end
local fp,msg = io.open(file,"r")
if fp == nil then print("error: " .. msg) os.exit(1) end
local buf = fp:read("*a")
fp:close()
buf = buf:gsub("\\bibitem%b[](%b{})","}\n\\footnotereference%1{")
buf = buf:gsub("\\bibitem(%b{})","}\n\\footnotereference%1{")
buf = buf:gsub("\\begin{thebibliography}%b{}[%s\n]*}","")
buf = buf:gsub("\\end{thebibliography}","}")
buf = buf:gsub("\n\n+","\n")

fp = io.open(file,"w")
fp:write(buf)
fp:close()

次のソースをsample.texとでもして保存．jpnbook.bibはTeX Wikiの文献データベースから．

\documentclass{jsarticle}
\makeatletter
\def\footnotereference#1#2{%
 \@namedef{footnote@reference@contents@#1}{#2}%
}
\def\@citex[#1]#2{\leavevmode
  \let\@citea\@empty
  \@for\@citeb:=#2\do
    {\@citea\def\@citea{,\penalty\@m\ }%
     \edef\@citeb{\expandafter\@firstofone\@citeb\@empty}%
     \if@filesw\immediate\write\@auxout{\string\citation{\@citeb}}\fi
     \@ifundefined{footnote@reference@contents@\@citeb}{\hbox{\reset@font\bfseries ?}%
       \G@refundefinedtrue
       \@latex@warning
         {Citation `\@citeb' on page \thepage \space undefined}}%
       {\footnote{\@nameuse{footnote@reference@contents@\@citeb}\if@tempswa , #1.\fi}}}}
\AtBeginDocument{\InputIfFileExists{\jobname.bbl}{}{}}
\makeatother
\begin{document}
\TeX ブック\cite{jtexbook}はなかなか買えない．
Lamport本\cite{jlatexbook}も買いにくくなってきている．

\bibliography{jpnbook}
\bibliographystyle{jplain}
\end{document}

次を実行．

> platex sample.tex
> pbibtex sample
> texlua bbl.lua sample
> platex sample
> dvipdfmx sample.dvi

こんなんができる．