Wouldn't people who knew their tools perfectly well not even use a cloud service like BigQuery? At the level you expect them to use the tool, they could have created a big query engine themselves. Isn't the whole point of these tools is to make things easier?
Sorry but that's nonsense. Partitioning is THE central cost controlling mechanism in BigQuery and the docs clearly state this. And it's an easy to use feature, so I'm not sure what makes you think using that would be as challenging as building your own query engine.