As an ESP, how much of a headache will this be for you in weeks/months to come? I'm guessing this throws a huge wrench in deliverability techniques--how're you handling it?
The reason why this is so nasty is not because Gmail went down, but because they returned a 5XX permanent failure and not a 4XX temporary failure for these bounces. Literally every email provider will respond to a permanent bounce by suppressing all further emails to that email address (it's permanent, after all!), so the fallout from this will be huge.
I logged into our sendgrid and mailgun accounts and manually purged all the failed gmail records.
Customers generally cannot change this on their end as far as I can imagine -- this is on the ESP end and is a protection built in because you are sending from their IP / Server and they don't take kindly to that.
The action for rectifying isn't too difficult, but the implications are still pretty big...