Custom error messages outside public directories


So I used The .htaccess way to create my error pages, and it works great.

However, I would like to place them in the root of my server.

My web directory is:
| /home/user/subdomains/www/www/

The files are currently placed in:
| /home/user/subdomains/www/www/err/
which means I can see them at:

The goal is to place them in:
| /home/user/err

That way:
[]They can be shared accross my subdomains
]They cannot be accessed directly by typing a URL

Is this doable or am I asking for too much?