Sim, isso é possível, especificando um local de raiz diferente,
-r, --root Specify an alternative installation root (default is /). This should not be used as a way to install software into /usr/local instead of /usr. This option is used if you want to install a package on a temporary mounted partition that is "owned" by another system. NOTE: if database path or logfile are not specified on either the command line or in pacman.conf(5), their default location will be inside this root path.