Thomas, I am watching with great interest your developments on opkg. Here are a few things I DETEST about ipkg, in case you are soliciting feature requests:
opkg should be smarter about non-default installation paths. ipkg-link works well enough most of the time, but when post-install scripts are run by ipkg, those scripts might be looking for files in /etc or /usr/share that don't exist because they aren't yet linked (user hasn't run ipkg-link yet).
on a related note, if installing a package also results in the installation of dependencies, opkg might be smarter about where it puts those (e.g., some system libraries in main flash, app libraries on card, etc.)
better still, maybe opkg.conf should allow different default locations for different types of packages, so I don't need to remember "-d card" every time
ipkg command-line options use a single dash for both one-letter options (e.g. "-d") and long options (e.g. "-force-reinstall"), contrary to nearly every other program in the world.
ipkg doesn't seem to handle very well the situation where one package is deprecated in favor of another that provides the same files/functions. I had some manual work to do when gtk+ package was dropped in favor of gtk+-fastscaling, for example.