Unfortunately, the source of the metapackage, mp-fremantle-generic-pr, is not available.
.... However, not everybody has got the CSSU installed, so this is no option (or I have to make this updated BusyBox depend on the CSSU).
The problem with this is that only one BusyBox binary can be installed (as there is just one /bin/busybox). I either have to make my package available as an alternative shell (which invalidates the whole 'replacement' thing), or the packages would overwrite each other their binaries.