I’ll mark this as answered, as I solved my problem and no other comments or answers were given:
Edit 1 – Alternative 1 answers the original question
BUT I had to learn that customized password salting is a legacy approach that is not needed in Spring Security 3.1 any more, as I describe in
Edit 3 where I left some pointers on how to use the StandardPasswordEncoder for automated Salts that are stored with the password.