Is it possible to create users home directories in /home instead of /var/www?
No. The base directory for apache suexec is compiled into the apache binaries of all Linux distributions and suecxec wont work in other directories then /var/www, so all website directories vahe to be a subdirectory of /var/www.
The link you posted above is for a different software. ISPConfig 2 is not ispconfig 3, the only thing they share is the name.