(1) Provide a port / package analog to misc/compat4x (misc/compatdf12 ?).
For the mean time, it could be automatically installed with the LiveCD.
(2) Push them as binaries into src/lib/compat or so and install them
with the normal world.
I strongly prefer (1), Matt prefers (2). The argument for (2) is the
self-contained nature of the CVS repo, the argument for (1) is less
bloat and that the same mechanism is used by FreeBSD. Once you have
all your packages converted, you can do a simple pkg_delete and be done.