How did you plan to achieve the characteristic of being expensive/upscalable to compute (mine), and cheap and quick to validate?

Also, how to avoid having vast amounts of data in the blockchain? A rather natural design in the given context might be based on training model parameters on some input data towards sufficiently low loss, so block validators only need to infer and check. But for alignment with real AI/ML workloads, the input and model parameter data would be huge.