Christoph, belier really looks like a hack. It’s easy to use ProxyCommand to connect to hosts using several hops.
Let’s say that you want to connect to host c, which can only be reached from host b, which can only be reached from host a. It’s as simple as doing:
Host a User logina Host b ProxyCommand ssh a nc -q 1 b 22 User loginb Host c ProxyCommand ssh b nc -q 1 b 22 User loginc
And of course, it just works with scp, rsync, and everything ssh-based.
It cannot auto-login using passwords, but I’m not sure that having passwords in clear text is a good idea either;)