HitmanDeadMan: Saints Row The Third: The Full Package does not live up to it's name. Unlockable Pack and Bloodsucker Pack are missing both here and in the Steam version of the package.
I'd also like to point out that Hitman 2: Silent Assassin is missing a patch BUT I can't find any info on whether said patch does anything other than censor the game by cutting out some dialogue and a turban.
Actually I asked this question long time ago, truth is, it was disabled in the full package version, as that dlc caused a gamebreaking bug, and was thus disabled.
Still, you should be able to force enable it by editing the GOG.ini file, look for bloodusucker and switch from disabled to enabled (can't really remember quite well, as it has been so long).
As for the gamebreaking bug part, I'm not really sure what it was, I only remember that it prevented something from completition.