Sure they can. They want to run a job, they can get the key from me and run it. This can be transparent to me; eg my phone could transmit them the key every day

Sure they can. They want to run a job, they can get the key from me and run it. This can be transparent to me; eg my phone could transmit them the key every day until I decide to stop. So many people are saying "your proposal breaks cloud services or requires client side compute", but that's not true. Be more imaginative and get outside the current model.