No offense Brother i though you were not aware of VPN. Please don't get confuse with the VPN type. whether road warrior or site to site openvpn. if site 2 site work then road warrior will definitely work. i find no reason for not providing Road Warrior/VPN on GCE, they provide OS and you can install whatever you want, though you will not get GUI in openvpn package alone. people are commonly use to configure openvpn on GUI firewalls like ipcop and pfsense etc. alternatively here you have to use CLI a bit uncomfortable mode for GUI users but the beauty of linux is CLI for sure :). its not hard to configure use easy-rsa script. even pptp, l2tp/ipsec, microsoft VPN, and all other vpn protocol will work. Google Just provide you a platform and you are the one who has to set it the way you want. Google give you just Full Linux version of your choice.
I hope that helps.