Ludo,
No, rsync-bpc isn't usable without BackupPC. Your name sounds fine (although it would be good to have a consistent package name across others flavors - are there any already?).
No, 3.1.2 isn't ready for use.
The main upgrade risk area is around rsync config parameters and arguments not being compatible between 3.x and 4.x. Configure.pl tries to extract $Conf{RsyncSshArgs} (a new 4.x setting) from the old $Conf{RsyncClientCmd} setting.
Craig