What about spreading your K8s load across multiple instance types (given it is unlikely google runs out of all types at the same time). That plus historical modeling was the trick of a startup that Amazon acquired that promised to dramatically reduce compute cost, by using mostly spot instances.
Would those types of mitigations work similarly with Google's premetable VM's?
Compute Engine doesn't really have "Instance Types" or "Instance Families" per say, just Core/Memory combinations. Larger machines have a higher chance of preemption though (according to the PM of PVMs who stated that on this thread).
There are a few interesting projects out there that do the kind of automation you are speaking of like these:
Would those types of mitigations work similarly with Google's premetable VM's?