This should have another option IMO when building from scripts on a clean vm since that build would probably not have ens33 set at the start right? More likely it would have eth0 I guess.

# Set correct interface
sed -i "s|ens33|$IFACE|g" /etc/network/interfaces
service networking restart

Something like if /etc/network/interfaces has ens33 then change it to IFACE else, leave it.