Sweave: multiple graphic formats, e.g. win.metafile

Dear R devel,

being constrained to a windows environment at work and having colleagues being accustomed to the Microsoft Office Suite, I was looking for a way to have the RweaveLatex driver for Sweave automatically generating 'win.metafile's in addition to the pdf graphics.
Without this functionalilty, the generation of emf-graphics is quite laborious, I think:

<<>>=
plotit <- function () {
  # code which generates the graphic
}
win.metafile("foobar.emf")
plotit()
dev.off()
pdf("foobar.pdf")
plotit()
dev.off()
@
\includegraphics{foobar}


I would like to have something like:

<<foobar, fig=true, pdf=true, emf=true>>
# code which generates the graphic
@


SweaveHooks are not applicable for this feature. Therefore, I thought it would be best to extend the typical 'RweaveLatex' driver by an option 'emf' - like eps and pdf. So, here is the result of some handicrafts:

RweaveLatexEMF <- function ()
{
	# add option emf (= FALSE) and set default for eps to FALSE
	setup <- utils::RweaveLatexSetup
	setupsrc <- deparse(setup)
	epsline <- grep("eps", setupsrc)
	setupsrc[epsline] <- sub("eps = TRUE", "eps = FALSE, emf = FALSE", setupsrc[epsline])
	setup <- eval(parse(text=setupsrc))

	# 'makeRweaveLatexCodeRunner' function
	makeruncode <- function(evalFunc=utils::RweaveEvalWithOpt) {
		runcode <- utils:::RweaveLatexRuncode
		runcodesrc <- deparse(runcode)
		epsline1 <- grep("cat(.. eps..)", runcodesrc)
		runcodesrc <- append(runcodesrc, "            if (options$emf) cat(\" emf\")", after=epsline1)
		epsline2 <- grep("options\\$fig && options\\$eval", runcodesrc)
		runcodesrc <- append(runcodesrc,
			deparse(quote(
				if (options$emf && .Platform$OS.type == "windows") {
		            grDevices::win.metafile(file=paste(chunkprefix, "emf", sep="."),
					                        width=options$width, height=options$height)
		            err <- try({SweaveHooks(options, run=TRUE)
		                        eval(chunkexps, envir=.GlobalEnv)})
		            grDevices::dev.off()
		            if(inherits(err, "try-error")) stop(err)
		        }
			))
		, after=epsline2)
		runcode <- eval(parse(text=runcodesrc))
	}
	runcode <- makeruncode()

	list(setup = setup, runcode = runcode,
       writedoc = utils::RweaveLatexWritedoc, finish = utils::RweaveLatexFinish,
       checkopts = utils::RweaveLatexOptions)
}


This enhanced Sweave driver works for me like a charm, but it is a very poor solution.
What about allowing for all available grDevices on the current platform - besides the standard eps and pdf devices? The only building block is the section "if (options$fig && options$eval)" in utils:::makeRweaveLatexCodeRunner. The TODO list of Seth Falcon's weaver package also states "For Sweave: multiple graphic formats besides just pdf and eps (perhaps
as a separate driver?)".
However, since so many packages depend on the basic Sweave implementation by Fritz Leisch, I don't know if there is an easy route to tackle.

Looking forward to your opinions and pointers.
Best regards,
 Sebastian Meyer