--exit-on-error is not supported by the busybox run-parts
and the easiest way is to make the ignore-errors option
the default.
I didn't test the change on the device but is looks sound.
This way we can manage bridges and vlans without additional
hacks. This package shouldn't clash with busybox so I need
to install all files with a ${BPN} suffix and then use the
update-alternatives to create the symlinks. The last two parts
were not tested/verified yet.