Re: make a hasty move to another region
Moving infrastructure might be easy. Google's forwarding rules come in two types, regional forwarding rules and global forwarding rules (anycast). The latter would be reasonably easy to set up a new backend to the LB in another region, that's what they're designed for to serve from the closest region to the client. But your persistent data is now going to be in another region incurring latency and financial penalties, or you need to move your persistent data too and incur downtime.
With the former regional forwarding rules you're screwed, you'll need to build another LB with another IP address and update your DNS as well as the former mentioned practical issues.