I don't quite get what you mean by "system into utf-8 encoding". You can
have UTF-8 filenames in UFS (and AFAIK almost all other file systems,
with exception of msdosfs), and there will be no corruption.
Problems you will almost certainly encounter are:
- bogus / wrong sorting (FreeBSD's locale data for utf-8 is very lacking)=
- the console (text-mode) doesn't support utf-8 so you'll see "garbage"
on it
- problems with Samba (more) and NFS (less, if the destination system is
configured to interpret file names as utf-8).