I suppose you could use montavista linux to start building dpkg and get
a chroot going a package at a time and building everything big endian
(you would have to add a new target to dpkg called armeb probably [mips
and mipsel are mips endian big and mips endian little respectively, so
arm and armeb make some sense that way) and add whatever uname -m calls
the system to the archtable. After the first few base packages are
compiled and installed in a chroot, you might be able to have it build
everything else you want as debian packages and start using it. Of
course debian arm packages won't work, you will have to recompile all of
them for armeb (including updated which architectures packages should
compile on at all if something lists arm explicitly). It would be a lot
of work.