Ranger,
You paint a very grim picture of Austrian electrical installations.
I don't like the panel without cover, it would be easy for someone to accidentally put their fingers into the back.
I have to agree with djk's comments on fusing the neutral, this has been prohibited in the UK for over 50 years. It would be acceptable to install a multi-pole linked breaker that also breaks the associated phase(s), but that is almost non-existent here.
As for the water heater connection, how could anyone leave such a bodge where it is accessible to members of the public, even if it was just a temporary connection.
